644693641 has 8 divisors (see below), whose sum is σ = 657630720. Its totient is φ = 631876128.

The previous prime is 644693633. The next prime is 644693681. The reversal of 644693641 is 146396446.

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

It is not a de Polignac number, because 644693641 - 2³ = 644693633 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644693681) 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, 18961 + ... + 40606.

It is an arithmetic number, because the mean of its divisors is an integer number (82203840).

Almost surely, 2^644693641 is an apocalyptic number.

It is an amenable number.

644693641 is a deficient number, since it is larger than the sum of its proper divisors (12937079).

644693641 is a wasteful number, since it uses less digits than its factorization.

644693641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59783.

The product of its digits is 373248, while the sum is 43.

The square root of 644693641 is about 25390.8180451123. The cubic root of 644693641 is about 863.8754433106.

The spelling of 644693641 in words is "six hundred forty-four million, six hundred ninety-three thousand, six hundred forty-one".