644978 has 8 divisors (see below), whose sum is σ = 972972. Its totient is φ = 320656.

The previous prime is 644977. The next prime is 644999. The reversal of 644978 is 879446.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 644809 + 169 = 803^2 + 13^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (644977) 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, 425 + ... + 1212.

2⁶⁴⁴⁹⁷⁸ is an apocalyptic number.

644978 is a deficient number, since it is larger than the sum of its proper divisors (327994).

644978 is a wasteful number, since it uses less digits than its factorization.

644978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1836.

The product of its digits is 48384, while the sum is 38.

The square root of 644978 is about 803.1052234919. The cubic root of 644978 is about 86.4002436264.

The spelling of 644978 in words is "six hundred forty-four thousand, nine hundred seventy-eight".