644176381 has 2 divisors, whose sum is σ = 644176382. Its totient is φ = 644176380.

The previous prime is 644176369. The next prime is 644176417. The reversal of 644176381 is 183671446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 482505156 + 161671225 = 21966^2 + 12715^2 .

It is a cyclic number.

It is not a de Polignac number, because 644176381 - 2²⁹ = 107305469 is a prime.

It is a super-2 number, since 2×644176381² = 829926419676514322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644176301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322088190 + 322088191.

It is an arithmetic number, because the mean of its divisors is an integer number (322088191).

Almost surely, 2^644176381 is an apocalyptic number.

It is an amenable number.

644176381 is a deficient number, since it is larger than the sum of its proper divisors (1).

644176381 is an equidigital number, since it uses as much as digits as its factorization.

644176381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 96768, while the sum is 40.

The square root of 644176381 is about 25380.6300355212. The cubic root of 644176381 is about 863.6443424466.

The spelling of 644176381 in words is "six hundred forty-four million, one hundred seventy-six thousand, three hundred eighty-one".