644269393 has 2 divisors, whose sum is σ = 644269394. Its totient is φ = 644269392.

The previous prime is 644269361. The next prime is 644269433. The reversal of 644269393 is 393962446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 379003024 + 265266369 = 19468^2 + 16287^2 .

It is a cyclic number.

It is not a de Polignac number, because 644269393 - 2⁵ = 644269361 is a prime.

It is not a weakly prime, because it can be changed into another prime (644269303) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322134696 + 322134697.

It is an arithmetic number, because the mean of its divisors is an integer number (322134697).

Almost surely, 2^644269393 is an apocalyptic number.

It is an amenable number.

644269393 is a deficient number, since it is larger than the sum of its proper divisors (1).

644269393 is an equidigital number, since it uses as much as digits as its factorization.

644269393 is an evil number, because the sum of its binary digits is even.

The product of its digits is 839808, while the sum is 46.

The square root of 644269393 is about 25382.4623116040. The cubic root of 644269393 is about 863.6859073678.

Adding to 644269393 its product of digits (839808), we get a square (645109201 = 25399²).

The spelling of 644269393 in words is "six hundred forty-four million, two hundred sixty-nine thousand, three hundred ninety-three".