645515657 has 2 divisors, whose sum is σ = 645515658. Its totient is φ = 645515656.

The previous prime is 645515639. The next prime is 645515681. The reversal of 645515657 is 756515546.

645515657 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 392673856 + 252841801 = 19816^2 + 15901^2 .

It is a cyclic number.

It is not a de Polignac number, because 645515657 - 2²⁰ = 644467081 is a prime.

It is not a weakly prime, because it can be changed into another prime (645515617) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322757828 + 322757829.

It is an arithmetic number, because the mean of its divisors is an integer number (322757829).

Almost surely, 2^645515657 is an apocalyptic number.

It is an amenable number.

645515657 is a deficient number, since it is larger than the sum of its proper divisors (1).

645515657 is an equidigital number, since it uses as much as digits as its factorization.

645515657 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 630000, while the sum is 44.

The square root of 645515657 is about 25407.0001574369. Note that the first 3 decimals coincide. The cubic root of 645515657 is about 864.2424485528.

The spelling of 645515657 in words is "six hundred forty-five million, five hundred fifteen thousand, six hundred fifty-seven".