644601972 has 96 divisors (see below), whose sum is σ = 1799225344. Its totient is φ = 175737600.

The previous prime is 644601967. The next prime is 644602033. The reversal of 644601972 is 279106446.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 644601972.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 188397 + ... + 191787.

Almost surely, 2^644601972 is an apocalyptic number.

644601972 is a gapful number since it is divisible by the number (62) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644601972, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (899612672).

644601972 is an abundant number, since it is smaller than the sum of its proper divisors (1154623372).

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

644601972 is a wasteful number, since it uses less digits than its factorization.

644601972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3509 (or 3507 counting only the distinct ones).

The product of its (nonzero) digits is 72576, while the sum is 39.

The square root of 644601972 is about 25389.0128205096. The cubic root of 644601972 is about 863.8344965483.

The spelling of 644601972 in words is "six hundred forty-four million, six hundred one thousand, nine hundred seventy-two".