644101972 has 12 divisors (see below), whose sum is σ = 1127388276. Its totient is φ = 321991040.

The previous prime is 644101943. The next prime is 644101981. The reversal of 644101972 is 279101446.

It can be written as a sum of positive squares in 2 ways, for example, as 496576656 + 147525316 = 22284^2 + 12146^2 .

It is a congruent number.

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, 16572 + ... + 39532.

It is an arithmetic number, because the mean of its divisors is an integer number (93949023).

Almost surely, 2^644101972 is an apocalyptic number.

It is an amenable number.

644101972 is a deficient number, since it is larger than the sum of its proper divisors (483286304).

644101972 is a wasteful number, since it uses less digits than its factorization.

644101972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29978 (or 29976 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 644101972 is about 25379.1641312317. The cubic root of 644101972 is about 863.6110878969.

The spelling of 644101972 in words is "six hundred forty-four million, one hundred one thousand, nine hundred seventy-two".