640564638 has 32 divisors (see below), whose sum is σ = 1465440000. Its totient is φ = 182856960.

The previous prime is 640564637. The next prime is 640564643. The reversal of 640564638 is 836465046.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 640564638.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640564633) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 46353 + ... + 58563.

It is an arithmetic number, because the mean of its divisors is an integer number (45795000).

Almost surely, 2^640564638 is an apocalyptic number.

640564638 is an abundant number, since it is smaller than the sum of its proper divisors (824875362).

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

640564638 is a wasteful number, since it uses less digits than its factorization.

640564638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13472.

The product of its (nonzero) digits is 414720, while the sum is 42.

The square root of 640564638 is about 25309.3784593775. The cubic root of 640564638 is about 862.0272339556.

The spelling of 640564638 in words is "six hundred forty million, five hundred sixty-four thousand, six hundred thirty-eight".