644673019 has 2 divisors, whose sum is σ = 644673020. Its totient is φ = 644673018.

The previous prime is 644672969. The next prime is 644673041. The reversal of 644673019 is 910376446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644673019 - 2⁹ = 644672507 is a prime.

It is a super-2 number, since 2×644673019² = 831206602853148722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (644673319) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322336509 + 322336510.

It is an arithmetic number, because the mean of its divisors is an integer number (322336510).

Almost surely, 2^644673019 is an apocalyptic number.

644673019 is a deficient number, since it is larger than the sum of its proper divisors (1).

644673019 is an equidigital number, since it uses as much as digits as its factorization.

644673019 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 108864, while the sum is 40.

The square root of 644673019 is about 25390.4119501831. The cubic root of 644673019 is about 863.8662322020.

The spelling of 644673019 in words is "six hundred forty-four million, six hundred seventy-three thousand, nineteen".