645312409 has 27 divisors (see below), whose sum is σ = 796427541. Its totient is φ = 521269560.

The previous prime is 645312391. The next prime is 645312431. The reversal of 645312409 is 904213546.

It is a happy number.

The square root of 645312409 is 25403.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 645312409 - 2¹³ = 645304217 is a prime.

It is not an unprimeable number, because it can be changed into a prime (645312509) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 3378504 + ... + 3378694.

Almost surely, 2^645312409 is an apocalyptic number.

645312409 is the 25403-rd square number.

645312409 is the 12702-nd centered octagonal number.

It is an amenable number.

645312409 is a deficient number, since it is larger than the sum of its proper divisors (151115132).

645312409 is an equidigital number, since it uses as much as digits as its factorization.

645312409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 434 (or 217 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 34.

The cubic root of 645312409 is about 864.1517334858.

The spelling of 645312409 in words is "six hundred forty-five million, three hundred twelve thousand, four hundred nine".