644976 has 40 divisors (see below), whose sum is σ = 1852560. Its totient is φ = 214848.

The previous prime is 644951. The next prime is 644977. The reversal of 644976 is 679446.

644976 is a `hidden beast` number, since 644 + 9 + 7 + 6 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 644976.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644977) by changing a digit.

644976 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 in 7 ways as a sum of consecutive naturals, for example, 315 + ... + 1178.

It is an arithmetic number, because the mean of its divisors is an integer number (46314).

2⁶⁴⁴⁹⁷⁶ is an apocalyptic number.

It is an amenable number.

644976 is an abundant number, since it is smaller than the sum of its proper divisors (1207584).

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

644976 is a wasteful number, since it uses less digits than its factorization.

644976 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1510 (or 1498 counting only the distinct ones).

The product of its digits is 36288, while the sum is 36.

The square root of 644976 is about 803.1039783241. The cubic root of 644976 is about 86.4001543207.

The spelling of 644976 in words is "six hundred forty-four thousand, nine hundred seventy-six".