644648 has 16 divisors (see below), whose sum is σ = 1229460. Its totient is φ = 316800.

The previous prime is 644647. The next prime is 644653. The reversal of 644648 is 846446.

It can be written as a sum of positive squares in 2 ways, for example, as 643204 + 1444 = 802^2 + 38^2 .

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644648.

It is not an unprimeable number, because it can be changed into a prime (644647) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 173 + ... + 1148.

2⁶⁴⁴⁶⁴⁸ is an apocalyptic number.

It is an amenable number.

644648 is a deficient number, since it is larger than the sum of its proper divisors (584812).

644648 is a wasteful number, since it uses less digits than its factorization.

644648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1388 (or 1384 counting only the distinct ones).

The product of its digits is 18432, while the sum is 32.

The square root of 644648 is about 802.8997446755. The cubic root of 644648 is about 86.3855056847.

Adding to 644648 its sum of digits (32), we get a triangular number (644680 = T₁₁₃₅).

The spelling of 644648 in words is "six hundred forty-four thousand, six hundred forty-eight".