645691031 has 2 divisors, whose sum is σ = 645691032. Its totient is φ = 645691030.

The previous prime is 645691021. The next prime is 645691043. The reversal of 645691031 is 130196546.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 645691031 - 2¹⁰ = 645690007 is a prime.

It is a super-2 number, since 2×645691031² = 833833815027685922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 645690982 and 645691000.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645691021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322845515 + 322845516.

It is an arithmetic number, because the mean of its divisors is an integer number (322845516).

Almost surely, 2^645691031 is an apocalyptic number.

645691031 is a deficient number, since it is larger than the sum of its proper divisors (1).

645691031 is an equidigital number, since it uses as much as digits as its factorization.

645691031 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 19440, while the sum is 35.

The square root of 645691031 is about 25410.4512159859. The cubic root of 645691031 is about 864.3207073989.

The spelling of 645691031 in words is "six hundred forty-five million, six hundred ninety-one thousand, thirty-one".