640955631 has 16 divisors (see below), whose sum is σ = 866154240. Its totient is φ = 421545600.

The previous prime is 640955629. The next prime is 640955669. The reversal of 640955631 is 136559046.

It is not a de Polignac number, because 640955631 - 2¹ = 640955629 is a prime.

It is a super-2 number, since 2×640955631² = 821648241821216322, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 640955631.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640955681) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 227431 + ... + 230231.

It is an arithmetic number, because the mean of its divisors is an integer number (54134640).

Almost surely, 2^640955631 is an apocalyptic number.

640955631 is a deficient number, since it is larger than the sum of its proper divisors (225198609).

640955631 is a wasteful number, since it uses less digits than its factorization.

640955631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3806.

The product of its (nonzero) digits is 97200, while the sum is 39.

The square root of 640955631 is about 25317.1015521130. The cubic root of 640955631 is about 862.2025886563.

The spelling of 640955631 in words is "six hundred forty million, nine hundred fifty-five thousand, six hundred thirty-one".