640081931 has 2 divisors, whose sum is σ = 640081932. Its totient is φ = 640081930.

The previous prime is 640081921. The next prime is 640081963. The reversal of 640081931 is 139180046.

It is a happy number.

It is an a-pointer prime, because the next prime (640081963) can be obtained adding 640081931 to its sum of digits (32).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 640081931 - 2⁶ = 640081867 is a prime.

It is a super-2 number, since 2×640081931² = 819409756785377522, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (640081921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320040965 + 320040966.

It is an arithmetic number, because the mean of its divisors is an integer number (320040966).

Almost surely, 2^640081931 is an apocalyptic number.

640081931 is a deficient number, since it is larger than the sum of its proper divisors (1).

640081931 is an equidigital number, since it uses as much as digits as its factorization.

640081931 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5184, while the sum is 32.

The square root of 640081931 is about 25299.8405330943. The cubic root of 640081931 is about 861.8106483996.

The spelling of 640081931 in words is "six hundred forty million, eighty-one thousand, nine hundred thirty-one".