644624 has 10 divisors (see below), whose sum is σ = 1248990. Its totient is φ = 322304.

The previous prime is 644617. The next prime is 644629. The reversal of 644624 is 426446.

It can be written as a sum of positive squares in only one way, i.e., 640000 + 4624 = 800^2 + 68^2 .

It is a junction number, because it is equal to n+sod(n) for n = 644593 and 644602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20129 + ... + 20160.

It is an arithmetic number, because the mean of its divisors is an integer number (124899).

2⁶⁴⁴⁶²⁴ is an apocalyptic number.

It is an amenable number.

644624 is a deficient number, since it is larger than the sum of its proper divisors (604366).

644624 is a wasteful number, since it uses less digits than its factorization.

644624 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40297 (or 40291 counting only the distinct ones).

The product of its digits is 4608, while the sum is 26.

The square root of 644624 is about 802.8847987103. The cubic root of 644624 is about 86.3844336383.

It can be divided in two parts, 644 and 624, that multiplied together give a triangular number (401856 = T₈₉₆).

The spelling of 644624 in words is "six hundred forty-four thousand, six hundred twenty-four".