644377989 has 16 divisors (see below), whose sum is σ = 905036480. Its totient is φ = 406684800.

The previous prime is 644377973. The next prime is 644378011. The reversal of 644377989 is 989773446.

It is not a de Polignac number, because 644377989 - 2⁴ = 644377973 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (57).

It is a Duffinian number.

644377989 is a Rhonda number in base 6.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644377939) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 99519 + ... + 105795.

It is an arithmetic number, because the mean of its divisors is an integer number (56564780).

Almost surely, 2^644377989 is an apocalyptic number.

It is an amenable number.

644377989 is a deficient number, since it is larger than the sum of its proper divisors (260658491).

644377989 is a wasteful number, since it uses less digits than its factorization.

644377989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8100.

The product of its digits is 9144576, while the sum is 57.

The square root of 644377989 is about 25384.6014150311. The cubic root of 644377989 is about 863.7344313582.

The spelling of 644377989 in words is "six hundred forty-four million, three hundred seventy-seven thousand, nine hundred eighty-nine".