644485536 has 144 divisors (see below), whose sum is σ = 1944004608. Its totient is φ = 202176000.

The previous prime is 644485493. The next prime is 644485549. The reversal of 644485536 is 635584446.

It is a tau number, because it is divible by the number of its divisors (144).

It is a super-2 number, since 2×644485536² = 830723212226414592, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 644485491 and 644485500.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 329361 + ... + 331311.

It is an arithmetic number, because the mean of its divisors is an integer number (13500032).

Almost surely, 2^644485536 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 644485536, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (972002304).

644485536 is an abundant number, since it is smaller than the sum of its proper divisors (1299519072).

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

644485536 is a wasteful number, since it uses less digits than its factorization.

644485536 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2035 (or 2024 counting only the distinct ones).

The product of its digits is 1382400, while the sum is 45.

The square root of 644485536 is about 25386.7196778158. The cubic root of 644485536 is about 863.7824812508.

The spelling of 644485536 in words is "six hundred forty-four million, four hundred eighty-five thousand, five hundred thirty-six".