644435971 has 2 divisors, whose sum is σ = 644435972. Its totient is φ = 644435970.

The previous prime is 644435959. The next prime is 644436007. The reversal of 644435971 is 179534446.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644435971 - 2²¹ = 642338819 is a prime.

It is not a weakly prime, because it can be changed into another prime (644430971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322217985 + 322217986.

It is an arithmetic number, because the mean of its divisors is an integer number (322217986).

Almost surely, 2^644435971 is an apocalyptic number.

644435971 is a deficient number, since it is larger than the sum of its proper divisors (1).

644435971 is an equidigital number, since it uses as much as digits as its factorization.

644435971 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 362880, while the sum is 43.

The square root of 644435971 is about 25385.7434596665. The cubic root of 644435971 is about 863.7603372440.

The spelling of 644435971 in words is "six hundred forty-four million, four hundred thirty-five thousand, nine hundred seventy-one".