644624532 has 18 divisors (see below), whose sum is σ = 1629467658. Its totient is φ = 214874832.

The previous prime is 644624489. The next prime is 644624537. The reversal of 644624532 is 235426446.

644624532 is a `hidden beast` number, since 64 + 4 + 62 + 4 + 532 = 666.

It can be written as a sum of positive squares in only one way, i.e., 640798596 + 3825936 = 25314^2 + 1956^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 17906237 = 644624532 / (6 + 4 + 4 + 6 + 2 + 4 + 5 + 3 + 2).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644624537) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 8953083 + ... + 8953154.

It is an arithmetic number, because the mean of its divisors is an integer number (90525981).

Almost surely, 2^644624532 is an apocalyptic number.

It is an amenable number.

644624532 is an abundant number, since it is smaller than the sum of its proper divisors (984843126).

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

644624532 is a wasteful number, since it uses less digits than its factorization.

644624532 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17906247 (or 17906242 counting only the distinct ones).

The product of its digits is 138240, while the sum is 36.

The square root of 644624532 is about 25389.4571032939. The cubic root of 644624532 is about 863.8445740224.

The spelling of 644624532 in words is "six hundred forty-four million, six hundred twenty-four thousand, five hundred thirty-two".