644642239 has 2 divisors, whose sum is σ = 644642240. Its totient is φ = 644642238.

The previous prime is 644642213. The next prime is 644642249. The reversal of 644642239 is 932246446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644642239 - 2²⁷ = 510424511 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644642209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322321119 + 322321120.

It is an arithmetic number, because the mean of its divisors is an integer number (322321120).

Almost surely, 2^644642239 is an apocalyptic number.

644642239 is a deficient number, since it is larger than the sum of its proper divisors (1).

644642239 is an equidigital number, since it uses as much as digits as its factorization.

644642239 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 248832, while the sum is 40.

The square root of 644642239 is about 25389.8058086311. The cubic root of 644642239 is about 863.8524835134.

The spelling of 644642239 in words is "six hundred forty-four million, six hundred forty-two thousand, two hundred thirty-nine".