644708532 has 96 divisors (see below), whose sum is σ = 1712632320. Its totient is φ = 187125120.

The previous prime is 644708531. The next prime is 644708539. The reversal of 644708532 is 235807446.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644708531) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1312807 + ... + 1313297.

It is an arithmetic number, because the mean of its divisors is an integer number (17839920).

Almost surely, 2^644708532 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 644708532, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (856316160).

644708532 is an abundant number, since it is smaller than the sum of its proper divisors (1067923788).

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

644708532 is a wasteful number, since it uses less digits than its factorization.

644708532 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 973 (or 971 counting only the distinct ones).

The product of its (nonzero) digits is 161280, while the sum is 39.

The square root of 644708532 is about 25391.1112793434. Note that the first 3 decimals coincide. The cubic root of 644708532 is about 863.8820944646.

The spelling of 644708532 in words is "six hundred forty-four million, seven hundred eight thousand, five hundred thirty-two".