640964920638 has 16 divisors (see below), whose sum is σ = 1465062675840. Its totient is φ = 183132834456.

The previous prime is 640964920613. The next prime is 640964920643. The reversal of 640964920638 is 836029469046.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7630534728 + ... + 7630534811.

It is an arithmetic number, because the mean of its divisors is an integer number (91566417240).

Almost surely, 2^640964920638 is an apocalyptic number.

640964920638 is an abundant number, since it is smaller than the sum of its proper divisors (824097755202).

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

640964920638 is a wasteful number, since it uses less digits than its factorization.

640964920638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15261069551.

The product of its (nonzero) digits is 13436928, while the sum is 57.

The spelling of 640964920638 in words is "six hundred forty billion, nine hundred sixty-four million, nine hundred twenty thousand, six hundred thirty-eight".