640138956 has 48 divisors (see below), whose sum is σ = 1574160000. Its totient is φ = 201906432.

The previous prime is 640138951. The next prime is 640138969. The reversal of 640138956 is 659831046.

It is not an unprimeable number, because it can be changed into a prime (640138951) 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, 340836 + ... + 342708.

It is an arithmetic number, because the mean of its divisors is an integer number (32795000).

Almost surely, 2^640138956 is an apocalyptic number.

It is an amenable number.

640138956 is an abundant number, since it is smaller than the sum of its proper divisors (934021044).

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

640138956 is a wasteful number, since it uses less digits than its factorization.

640138956 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3398 (or 3396 counting only the distinct ones).

The product of its (nonzero) digits is 155520, while the sum is 42.

The square root of 640138956 is about 25300.9674913826. The cubic root of 640138956 is about 861.8362405884.

The spelling of 640138956 in words is "six hundred forty million, one hundred thirty-eight thousand, nine hundred fifty-six".