644596391 has 2 divisors, whose sum is σ = 644596392. Its totient is φ = 644596390.

The previous prime is 644596387. The next prime is 644596439. The reversal of 644596391 is 193695446.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644596391 - 2² = 644596387 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644596591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322298195 + 322298196.

It is an arithmetic number, because the mean of its divisors is an integer number (322298196).

Almost surely, 2^644596391 is an apocalyptic number.

644596391 is a deficient number, since it is larger than the sum of its proper divisors (1).

644596391 is an equidigital number, since it uses as much as digits as its factorization.

644596391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 699840, while the sum is 47.

The square root of 644596391 is about 25388.9029105237. The cubic root of 644596391 is about 863.8320034986.

The spelling of 644596391 in words is "six hundred forty-four million, five hundred ninety-six thousand, three hundred ninety-one".