644400319 has 2 divisors, whose sum is σ = 644400320. Its totient is φ = 644400318.

The previous prime is 644400313. The next prime is 644400343. The reversal of 644400319 is 913004446.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644400319 - 2³ = 644400311 is a prime.

It is a super-2 number, since 2×644400319² = 830503542254603522, which contains 22 as substring.

It is equal to p_33517273 and since 644400319 and 33517273 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644400311) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322200159 + 322200160.

It is an arithmetic number, because the mean of its divisors is an integer number (322200160).

Almost surely, 2^644400319 is an apocalyptic number.

644400319 is a deficient number, since it is larger than the sum of its proper divisors (1).

644400319 is an equidigital number, since it uses as much as digits as its factorization.

644400319 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10368, while the sum is 31.

The square root of 644400319 is about 25385.0412447961. The cubic root of 644400319 is about 863.7444084045.

The spelling of 644400319 in words is "six hundred forty-four million, four hundred thousand, three hundred nineteen".