645515110621 has 2 divisors, whose sum is σ = 645515110622. Its totient is φ = 645515110620.

The previous prime is 645515110613. The next prime is 645515110627. The reversal of 645515110621 is 126011515546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 551625571225 + 93889539396 = 742715^2 + 306414^2 .

It is a cyclic number.

It is not a de Polignac number, because 645515110621 - 2³ = 645515110613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645515110627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322757555310 + 322757555311.

It is an arithmetic number, because the mean of its divisors is an integer number (322757555311).

Almost surely, 2^645515110621 is an apocalyptic number.

It is an amenable number.

645515110621 is a deficient number, since it is larger than the sum of its proper divisors (1).

645515110621 is an equidigital number, since it uses as much as digits as its factorization.

645515110621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 36000, while the sum is 37.

The spelling of 645515110621 in words is "six hundred forty-five billion, five hundred fifteen million, one hundred ten thousand, six hundred twenty-one".