644291979 has 4 divisors (see below), whose sum is σ = 859055976. Its totient is φ = 429527984.

The previous prime is 644291971. The next prime is 644291981. The reversal of 644291979 is 979192446.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 644291979 - 2³ = 644291971 is a prime.

It is a super-2 number, since 2×644291979² = 830224308407472882, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (644291971) 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, 107381994 + ... + 107381999.

It is an arithmetic number, because the mean of its divisors is an integer number (214763994).

Almost surely, 2^644291979 is an apocalyptic number.

644291979 is a deficient number, since it is larger than the sum of its proper divisors (214763997).

644291979 is a wasteful number, since it uses less digits than its factorization.

644291979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214763996.

The product of its digits is 979776, while the sum is 51.

The square root of 644291979 is about 25382.9072211991. The cubic root of 644291979 is about 863.6959999275.

The spelling of 644291979 in words is "six hundred forty-four million, two hundred ninety-one thousand, nine hundred seventy-nine".