644706431 has 2 divisors, whose sum is σ = 644706432. Its totient is φ = 644706430.

The previous prime is 644706397. The next prime is 644706437. The reversal of 644706431 is 134607446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644706431 - 2⁶ = 644706367 is a prime.

It is a super-2 number, since 2×644706431² = 831292764345515522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a junction number, because it is equal to n+sod(n) for n = 644706391 and 644706400.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644706437) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322353215 + 322353216.

It is an arithmetic number, because the mean of its divisors is an integer number (322353216).

Almost surely, 2^644706431 is an apocalyptic number.

644706431 is a deficient number, since it is larger than the sum of its proper divisors (1).

644706431 is an equidigital number, since it uses as much as digits as its factorization.

644706431 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 48384, while the sum is 35.

The square root of 644706431 is about 25391.0699065636. The cubic root of 644706431 is about 863.8811560466.

The spelling of 644706431 in words is "six hundred forty-four million, seven hundred six thousand, four hundred thirty-one".