640255531 has 4 divisors (see below), whose sum is σ = 668092752. Its totient is φ = 612418312.

The previous prime is 640255501. The next prime is 640255541. The reversal of 640255531 is 135552046.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 640255531 - 2⁷ = 640255403 is a prime.

It is a super-2 number, since 2×640255531² = 819854289952183922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 640255493 and 640255502.

It is not an unprimeable number, because it can be changed into a prime (640255501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13918576 + ... + 13918621.

It is an arithmetic number, because the mean of its divisors is an integer number (167023188).

Almost surely, 2^640255531 is an apocalyptic number.

640255531 is a deficient number, since it is larger than the sum of its proper divisors (27837221).

640255531 is a wasteful number, since it uses less digits than its factorization.

640255531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27837220.

The product of its (nonzero) digits is 18000, while the sum is 31.

The square root of 640255531 is about 25303.2711521653. The cubic root of 640255531 is about 861.8885534290. Note that the first 3 decimals are identical.

The spelling of 640255531 in words is "six hundred forty million, two hundred fifty-five thousand, five hundred thirty-one".