640656713664 has 840 divisors, whose sum is σ = 2214673599600. Its totient is φ = 182659276800.

The previous prime is 640656713659. The next prime is 640656713717. The reversal of 640656713664 is 466317656046.

640656713664 is a `hidden beast` number, since 6 + 4 + 0 + 6 + 567 + 13 + 6 + 64 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a self number, because there is not a number n which added to its sum of digits gives 640656713664.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 119 ways as a sum of consecutive naturals, for example, 745816467 + ... + 745817325.

It is an arithmetic number, because the mean of its divisors is an integer number (2636516190).

Almost surely, 2^640656713664 is an apocalyptic number.

640656713664 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640656713664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1107336799800).

640656713664 is an abundant number, since it is smaller than the sum of its proper divisors (1574016885936).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640656713664 is a wasteful number, since it uses less digits than its factorization.

640656713664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 975 (or 945 counting only the distinct ones).

The product of its (nonzero) digits is 13063680, while the sum is 54.

The spelling of 640656713664 in words is "six hundred forty billion, six hundred fifty-six million, seven hundred thirteen thousand, six hundred sixty-four".