644972 has 12 divisors (see below), whose sum is σ = 1134336. Its totient is φ = 320880.

The previous prime is 644951. The next prime is 644977. The reversal of 644972 is 279446.

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

644972 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1322 + ... + 1742.

It is an arithmetic number, because the mean of its divisors is an integer number (94528).

2⁶⁴⁴⁹⁷² is an apocalyptic number.

It is an amenable number.

644972 is a deficient number, since it is larger than the sum of its proper divisors (489364).

644972 is a wasteful number, since it uses less digits than its factorization.

644972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 808 (or 806 counting only the distinct ones).

The product of its digits is 12096, while the sum is 32.

The square root of 644972 is about 803.1014879827. The cubic root of 644972 is about 86.3999757087.

The spelling of 644972 in words is "six hundred forty-four thousand, nine hundred seventy-two".