645125609 has 2 divisors, whose sum is σ = 645125610. Its totient is φ = 645125608.

The previous prime is 645125567. The next prime is 645125617. The reversal of 645125609 is 906521546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 567773584 + 77352025 = 23828^2 + 8795^2 .

It is a cyclic number.

It is not a de Polignac number, because 645125609 - 2²⁰ = 644077033 is a prime.

It is not a weakly prime, because it can be changed into another prime (645125659) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322562804 + 322562805.

It is an arithmetic number, because the mean of its divisors is an integer number (322562805).

Almost surely, 2^645125609 is an apocalyptic number.

It is an amenable number.

645125609 is a deficient number, since it is larger than the sum of its proper divisors (1).

645125609 is an equidigital number, since it uses as much as digits as its factorization.

645125609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 64800, while the sum is 38.

The square root of 645125609 is about 25399.3230027889. The cubic root of 645125609 is about 864.0683428056.

The spelling of 645125609 in words is "six hundred forty-five million, one hundred twenty-five thousand, six hundred nine".