644679 has 24 divisors (see below), whose sum is σ = 1106560. Its totient is φ = 367416.

The previous prime is 644671. The next prime is 644687. The reversal of 644679 is 976446.

644679 is a `hidden beast` number, since 644 + 6 + 7 + 9 = 666.

It is an interprime number because it is at equal distance from previous prime (644671) and next prime (644687).

It is not a de Polignac number, because 644679 - 2³ = 644671 is a prime.

It is a super-2 number, since 2×644679² = 831222026082, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644671) by changing a digit.

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, 1512 + ... + 1890.

2⁶⁴⁴⁶⁷⁹ is an apocalyptic number.

644679 is a deficient number, since it is larger than the sum of its proper divisors (461881).

644679 is an equidigital number, since it uses as much as digits as its factorization.

644679 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 401 (or 389 counting only the distinct ones).

The product of its digits is 36288, while the sum is 36.

The square root of 644679 is about 802.9190494689. The cubic root of 644679 is about 86.3868903721.

The spelling of 644679 in words is "six hundred forty-four thousand, six hundred seventy-nine".