644975144 has 16 divisors (see below), whose sum is σ = 1319267520. Its totient is φ = 293170480.

The previous prime is 644975117. The next prime is 644975183. The reversal of 644975144 is 441579446.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is a junction number, because it is equal to n+sod(n) for n = 644975095 and 644975104.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3664544 + ... + 3664719.

It is an arithmetic number, because the mean of its divisors is an integer number (82454220).

Almost surely, 2^644975144 is an apocalyptic number.

It is an amenable number.

644975144 is an abundant number, since it is smaller than the sum of its proper divisors (674292376).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644975144 is a wasteful number, since it uses less digits than its factorization.

644975144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7329280 (or 7329276 counting only the distinct ones).

The product of its digits is 483840, while the sum is 44.

The square root of 644975144 is about 25396.3608416639. The cubic root of 644975144 is about 864.0011609781.

The spelling of 644975144 in words is "six hundred forty-four million, nine hundred seventy-five thousand, one hundred forty-four".