644310257 has 4 divisors (see below), whose sum is σ = 653926896. Its totient is φ = 634693620.

The previous prime is 644310167. The next prime is 644310281. The reversal of 644310257 is 752013446.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 644310257 - 2⁸ = 644310001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644310757) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4808219 + ... + 4808352.

It is an arithmetic number, because the mean of its divisors is an integer number (163481724).

Almost surely, 2^644310257 is an apocalyptic number.

644310257 is a gapful number since it is divisible by the number (67) formed by its first and last digit.

It is an amenable number.

644310257 is a deficient number, since it is larger than the sum of its proper divisors (9616639).

644310257 is an equidigital number, since it uses as much as digits as its factorization.

644310257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9616638.

The product of its (nonzero) digits is 20160, while the sum is 32.

The square root of 644310257 is about 25383.2672640856. The cubic root of 644310257 is about 863.7041672837.

The spelling of 644310257 in words is "six hundred forty-four million, three hundred ten thousand, two hundred fifty-seven".