640781125638 has 32 divisors (see below), whose sum is σ = 1351192387200. Its totient is φ = 202025010816.

The previous prime is 640781125577. The next prime is 640781125651. The reversal of 640781125638 is 836521187046.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4469731 + ... + 4610862.

It is an arithmetic number, because the mean of its divisors is an integer number (42224762100).

Almost surely, 2^640781125638 is an apocalyptic number.

640781125638 is an abundant number, since it is smaller than the sum of its proper divisors (710411261562).

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

640781125638 is a wasteful number, since it uses less digits than its factorization.

640781125638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9081236.

The product of its (nonzero) digits is 1935360, while the sum is 51.

The spelling of 640781125638 in words is "six hundred forty billion, seven hundred eighty-one million, one hundred twenty-five thousand, six hundred thirty-eight".