640635091 has 2 divisors, whose sum is σ = 640635092. Its totient is φ = 640635090.

The previous prime is 640635053. The next prime is 640635101. The reversal of 640635091 is 190536046.

640635091 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640635091 is a prime.

It is not a weakly prime, because it can be changed into another prime (640635791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320317545 + 320317546.

It is an arithmetic number, because the mean of its divisors is an integer number (320317546).

Almost surely, 2^640635091 is an apocalyptic number.

640635091 is a deficient number, since it is larger than the sum of its proper divisors (1).

640635091 is an equidigital number, since it uses as much as digits as its factorization.

640635091 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 19440, while the sum is 34.

The square root of 640635091 is about 25310.7702569479. The cubic root of 640635091 is about 862.0588363757.

The spelling of 640635091 in words is "six hundred forty million, six hundred thirty-five thousand, ninety-one".