644332291 has 2 divisors, whose sum is σ = 644332292. Its totient is φ = 644332290.

The previous prime is 644332229. The next prime is 644332301. The reversal of 644332291 is 192233446.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644332291 - 2⁷ = 644332163 is a prime.

It is not a weakly prime, because it can be changed into another prime (644332391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322166145 + 322166146.

It is an arithmetic number, because the mean of its divisors is an integer number (322166146).

Almost surely, 2^644332291 is an apocalyptic number.

644332291 is a deficient number, since it is larger than the sum of its proper divisors (1).

644332291 is an equidigital number, since it uses as much as digits as its factorization.

644332291 is an evil number, because the sum of its binary digits is even.

The product of its digits is 31104, while the sum is 34.

The square root of 644332291 is about 25383.7012864554. The cubic root of 644332291 is about 863.7140127686.

The spelling of 644332291 in words is "six hundred forty-four million, three hundred thirty-two thousand, two hundred ninety-one".