644155232 has 48 divisors (see below), whose sum is σ = 1452713472. Its totient is φ = 275425920.

The previous prime is 644155207. The next prime is 644155243. The reversal of 644155232 is 232551446.

It is a hoax number, since the sum of its digits (32) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 100607 + ... + 106817.

It is an arithmetic number, because the mean of its divisors is an integer number (30264864).

Almost surely, 2^644155232 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644155232, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (726356736).

644155232 is an abundant number, since it is smaller than the sum of its proper divisors (808558240).

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

644155232 is a wasteful number, since it uses less digits than its factorization.

644155232 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6691 (or 6683 counting only the distinct ones).

The product of its digits is 28800, while the sum is 32.

The square root of 644155232 is about 25380.2133954780. The cubic root of 644155232 is about 863.6348908871.

The spelling of 644155232 in words is "six hundred forty-four million, one hundred fifty-five thousand, two hundred thirty-two".