640635531 has 8 divisors (see below), whose sum is σ = 904426704. Its totient is φ = 401967360.

The previous prime is 640635487. The next prime is 640635551. The reversal of 640635531 is 135536046.

640635531 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 640635531 - 2⁶ = 640635467 is a prime.

It is a super-2 number, since 2×640635531² = 820827767159303922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 640635492 and 640635501.

It is not an unprimeable number, because it can be changed into a prime (640635551) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6280690 + ... + 6280791.

It is an arithmetic number, because the mean of its divisors is an integer number (113053338).

Almost surely, 2^640635531 is an apocalyptic number.

640635531 is a deficient number, since it is larger than the sum of its proper divisors (263791173).

640635531 is a wasteful number, since it uses less digits than its factorization.

640635531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12561501.

The product of its (nonzero) digits is 32400, while the sum is 33.

The square root of 640635531 is about 25310.7789488984. The cubic root of 640635531 is about 862.0590337349.

The spelling of 640635531 in words is "six hundred forty million, six hundred thirty-five thousand, five hundred thirty-one".