644428 has 12 divisors (see below), whose sum is σ = 1164352. Its totient is φ = 311760.

The previous prime is 644411. The next prime is 644431. The reversal of 644428 is 824446.

644428 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a hoax number, since the sum of its digits (28) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 644396 and 644405.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2475 + ... + 2722.

2⁶⁴⁴⁴²⁸ is an apocalyptic number.

It is an amenable number.

644428 is a deficient number, since it is larger than the sum of its proper divisors (519924).

644428 is a wasteful number, since it uses less digits than its factorization.

644428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5232 (or 5230 counting only the distinct ones).

The product of its digits is 6144, while the sum is 28.

The square root of 644428 is about 802.7627295783. The cubic root of 644428 is about 86.3756775958.

The spelling of 644428 in words is "six hundred forty-four thousand, four hundred twenty-eight".