Question

若把所有小于999 的质数乘起来,所得结果的个位数字是什么?

Answer 1

楼上的网友回答比较复杂了！
其实这题比较简单，小于999的质数的乘积 M：
M =2*3*5*7.....=30*7*11 .....，它一定是10的倍数。
所以，乘积的个位数一定是0。

Answer 2

小于999的质数是：2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997
这些数的乘积是=19590340644999083431262508198206381046123972390589368223882605328968666316379870661851951648789482321596229559115436019149189529725215266728292282990852649023362731392404017939142010958261393634959471483757196721672243410067118516227661133135192488848989914892157188308679896875137439519338903968094905549750386407106033836586660683539201011635917900039904495065203299749542985993134669814805318474080581207891125910