646640431 has 2 divisors, whose sum is σ = 646640432. Its totient is φ = 646640430.

The previous prime is 646640389. The next prime is 646640503. The reversal of 646640431 is 134046646.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 646640431 - 2⁷ = 646640303 is a prime.

It is a super-2 number, since 2×646640431² = 836287694007731522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (646640831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323320215 + 323320216.

It is an arithmetic number, because the mean of its divisors is an integer number (323320216).

Almost surely, 2^646640431 is an apocalyptic number.

646640431 is a deficient number, since it is larger than the sum of its proper divisors (1).

646640431 is an equidigital number, since it uses as much as digits as its factorization.

646640431 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 41472, while the sum is 34.

The square root of 646640431 is about 25429.1256436394. The cubic root of 646640431 is about 864.7441215821.

The spelling of 646640431 in words is "six hundred forty-six million, six hundred forty thousand, four hundred thirty-one".