644805401 has 16 divisors (see below), whose sum is σ = 701825040. Its totient is φ = 590929920.

The previous prime is 644805389. The next prime is 644805407. The reversal of 644805401 is 104508446.

It can be written as a sum of positive squares in 8 ways, for example, as 62789776 + 582015625 = 7924^2 + 24125^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644805401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644805407) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 36665 + ... + 51321.

It is an arithmetic number, because the mean of its divisors is an integer number (43864065).

Almost surely, 2^644805401 is an apocalyptic number.

It is an amenable number.

644805401 is a deficient number, since it is larger than the sum of its proper divisors (57019639).

644805401 is a wasteful number, since it uses less digits than its factorization.

644805401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14764.

The product of its (nonzero) digits is 15360, while the sum is 32.

The square root of 644805401 is about 25393.0187453166. The cubic root of 644805401 is about 863.9253590819.

The spelling of 644805401 in words is "six hundred forty-four million, eight hundred five thousand, four hundred one".