644427139 has 2 divisors, whose sum is σ = 644427140. Its totient is φ = 644427138.

The previous prime is 644427131. The next prime is 644427191. The reversal of 644427139 is 931724446.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644427139 - 2³ = 644427131 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (644427131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322213569 + 322213570.

It is an arithmetic number, because the mean of its divisors is an integer number (322213570).

Almost surely, 2^644427139 is an apocalyptic number.

644427139 is a deficient number, since it is larger than the sum of its proper divisors (1).

644427139 is an equidigital number, since it uses as much as digits as its factorization.

644427139 is an evil number, because the sum of its binary digits is even.

The product of its digits is 145152, while the sum is 40.

The square root of 644427139 is about 25385.5695031646. The cubic root of 644427139 is about 863.7563912786.

The spelling of 644427139 in words is "six hundred forty-four million, four hundred twenty-seven thousand, one hundred thirty-nine".