646689431 has 2 divisors, whose sum is σ = 646689432. Its totient is φ = 646689430.

The previous prime is 646689391. The next prime is 646689443. The reversal of 646689431 is 134986646.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-646689431 is a prime.

It is a super-2 number, since 2×646689431² = 836414440334207522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (646689331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323344715 + 323344716.

It is an arithmetic number, because the mean of its divisors is an integer number (323344716).

Almost surely, 2^646689431 is an apocalyptic number.

646689431 is a deficient number, since it is larger than the sum of its proper divisors (1).

646689431 is an equidigital number, since it uses as much as digits as its factorization.

646689431 is an evil number, because the sum of its binary digits is even.

The product of its digits is 746496, while the sum is 47.

The square root of 646689431 is about 25430.0890875357. The cubic root of 646689431 is about 864.7659633918.

The spelling of 646689431 in words is "six hundred forty-six million, six hundred eighty-nine thousand, four hundred thirty-one".