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Talk:Digit sum

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84: 74: 53: 22: 183:σ(A+B)=σ(A)+σ(B); σ(A×B)=σ(A)×σ(B); σ(A)=, σ(2)=1,2,4,8,7,5 for j=0,1,2,3,4,5, respectively. σ(3)=1,3,9 for k=0,1 and k not smaller than 2, respectively. σ(4)=1,4,7 for j=0,1,2, respectively. σ(5)=1,5,7,8,4,2 for j=0,1,2,3,4,5, respectively. σ(6)=1,6,9 for k=0,1 and k not smaller than 2, respectively. σ(7)=1,7,4 for j=0,1,2, respectively. σ(8)=1,8 for j=0,1, respectively. 277:
The concept of a decimal digit sum is closely related to, but not the same as, the digital root, which is the result of repeatedly applying the digit sum operation until the remaining value is only a single digit.
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Would be nice if someone could add a more generalised rule to the mod 9 for base 10. I'm sure it would just be mod (base-1) but the answer could be more tricky to interpret. For example, in binary ds(101) = 10?
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to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the
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The digit sum and digital root aren't the same, as you can read in the Applications section of the article:
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https://web.archive.org/web/20060913155630/http://instruct1.cit.cornell.edu/courses/econ719/Edgeworth.pdf
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I added info by a doctor in metaphysical philosophy upon advice from another user on the numerology page.
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Suppose we want to find σ(314159265358979). Let us state some basic operations and some periodicities:
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Let σ(M) be the digit sum of positive integer M. We all know from casting nines that σ(9k+r)=r.
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It seems to me if S(n) is a digit sum of n (in any base), then for any a,b:
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For the example, 314159265358979=9m+5, and 2718281828459045=6k+5, so
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http://instruct1.cit.cornell.edu/courses/econ719/Edgeworth.pdf
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When you have finished reviewing my changes, please set the
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for additional information. I made the following changes:
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I cannot find any reference for this on the internet.
101:, a collaborative effort to improve the coverage of 364:using the archive tool instructions below. Editors 350:This message was posted before February 2018. 252:I was surprised that they're different pages 8: 19: 300:I have just modified one external link on 47: 49: 339:to let others know (documentation at 7: 95:This article is within the scope of 173:May I add some results for base 10? 38:It is of interest to the following 14: 437:Low-priority mathematics articles 304:. Please take a moment to review 115:Knowledge:WikiProject Mathematics 432:Start-Class mathematics articles 118:Template:WikiProject Mathematics 82: 72: 51: 20: 135:This article has been rated as 288:12:33, 25 September 2022 (UTC) 196:18:41, 16 September 2006 (UTC) 1: 418:01:27, 13 December 2016 (UTC) 268:04:55, 13 November 2011 (UTC) 215:22:37, 23 February 2009 (UTC) 109:and see a list of open tasks. 168:10:45, 23 October 2005 (UTC) 189:σ(314159265358979)=σ(5)=2. 453: 381:(last update: 5 June 2024) 297:Hello fellow Wikipedians, 248:combine with digital root? 243:18:05, 7 August 2009 (UTC) 230:S(a*b) <= S(a) * S(b) 227:S(a+b) <= S(a) + S(b) 134: 67: 46: 141:project's priority scale 293:External links modified 98:WikiProject Mathematics 28:This article is rated 362:regular verification 201:Adding sheree silver 121:mathematics articles 352:After February 2018 331:parameter below to 406:InternetArchiveBot 357:InternetArchiveBot 90:Mathematics portal 34:content assessment 382: 258:comment added by 155: 154: 151: 150: 147: 146: 444: 416: 407: 380: 379: 358: 346: 270: 123: 122: 119: 116: 113: 92: 87: 86: 76: 69: 68: 63: 55: 48: 31: 25: 24: 16: 452: 451: 447: 446: 445: 443: 442: 441: 422: 421: 410: 405: 373: 366:have permission 356: 340: 310:this simple FaQ 295: 280:Polish bookworm 253: 250: 222: 203: 190: 184: 160: 120: 117: 114: 111: 110: 88: 81: 61: 32:on Knowledge's 29: 12: 11: 5: 450: 448: 440: 439: 434: 424: 423: 400: 399: 392: 325: 324: 316:Added archive 294: 291: 249: 246: 221: 218: 202: 199: 193:69.158.119.184 188: 182: 175: 174: 159: 156: 153: 152: 149: 148: 145: 144: 133: 127: 126: 124: 107:the discussion 94: 93: 77: 65: 64: 56: 44: 43: 37: 26: 13: 10: 9: 6: 4: 3: 2: 449: 438: 435: 433: 430: 429: 427: 420: 419: 414: 409: 408: 397: 393: 390: 386: 385: 384: 377: 371: 367: 363: 359: 353: 348: 344: 338: 334: 330: 323: 319: 315: 314: 313: 311: 307: 303: 298: 292: 290: 289: 285: 281: 274: 271: 269: 265: 261: 257: 247: 245: 244: 240: 236: 231: 228: 225: 219: 217: 216: 212: 208: 200: 198: 197: 194: 187: 181: 178: 172: 171: 170: 169: 166: 157: 142: 138: 132: 129: 128: 125: 108: 104: 100: 99: 91: 85: 80: 78: 75: 71: 70: 66: 60: 57: 54: 50: 45: 41: 35: 27: 23: 18: 17: 404: 401: 376:source check 355: 349: 336: 332: 328: 326: 299: 296: 275: 272: 260:69.76.179.81 254:— Preceding 251: 232: 229: 226: 223: 220:Inequalities 204: 191: 185: 179: 176: 161: 137:Low-priority 136: 96: 62:Low‑priority 40:WikiProjects 343:Sourcecheck 235:94.113.5.84 112:Mathematics 103:mathematics 59:Mathematics 30:Start-class 426:Categories 413:Report bug 158:Generalise 396:this tool 389:this tool 302:Digit sum 165:Syndicate 402:Cheers.— 256:unsigned 207:Spring12 329:checked 306:my edit 139:on the 337:failed 36:scale. 276:: --> 333:true 284:talk 264:talk 239:talk 211:talk 370:RfC 347:). 335:or 320:to 131:Low 428:: 383:. 378:}} 374:{{ 345:}} 341:{{ 286:) 266:) 241:) 213:) 415:) 411:( 398:. 391:. 282:( 262:( 237:( 209:( 143:. 42::

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Syndicate
10:45, 23 October 2005 (UTC)
69.158.119.184
18:41, 16 September 2006 (UTC)
Spring12
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22:37, 23 February 2009 (UTC)
94.113.5.84
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18:05, 7 August 2009 (UTC)
unsigned
69.76.179.81
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04:55, 13 November 2011 (UTC)
Polish bookworm
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12:33, 25 September 2022 (UTC)

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