644669861 has 8 divisors (see below), whose sum is σ = 705088800. Its totient is φ = 584553040.

The previous prime is 644669843. The next prime is 644669863. The reversal of 644669861 is 168966446.

644669861 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a cyclic number.

It is not a de Polignac number, because 644669861 - 2¹⁸ = 644407717 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644669863) 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, 71051 + ... + 79608.

It is an arithmetic number, because the mean of its divisors is an integer number (88136100).

Almost surely, 2^644669861 is an apocalyptic number.

It is an amenable number.

644669861 is a deficient number, since it is larger than the sum of its proper divisors (60418939).

644669861 is a wasteful number, since it uses less digits than its factorization.

644669861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151059.

The product of its digits is 1492992, while the sum is 50.

The square root of 644669861 is about 25390.3497612774. The cubic root of 644669861 is about 863.8648216192.

The spelling of 644669861 in words is "six hundred forty-four million, six hundred sixty-nine thousand, eight hundred sixty-one".