644312667 has 8 divisors (see below), whose sum is σ = 904298560. Its totient is φ = 406934280.

The previous prime is 644312623. The next prime is 644312671. The reversal of 644312667 is 766213446.

It is a happy number.

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

It is not a de Polignac number, because 644312667 - 2¹⁰ = 644311643 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644312687) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5651809 + ... + 5651922.

It is an arithmetic number, because the mean of its divisors is an integer number (113037320).

Almost surely, 2^644312667 is an apocalyptic number.

644312667 is a deficient number, since it is larger than the sum of its proper divisors (259985893).

644312667 is a wasteful number, since it uses less digits than its factorization.

644312667 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11303753.

The product of its digits is 145152, while the sum is 39.

The square root of 644312667 is about 25383.3147362593. The cubic root of 644312667 is about 863.7052441585.

It can be divided in two parts, 6443 and 12667, that added together give a triangular number (19110 = T₁₉₅).

The spelling of 644312667 in words is "six hundred forty-four million, three hundred twelve thousand, six hundred sixty-seven".