644491371 has 4 divisors (see below), whose sum is σ = 859321832. Its totient is φ = 429660912.

The previous prime is 644491361. The next prime is 644491409. The reversal of 644491371 is 173194446.

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

It is not a de Polignac number, because 644491371 - 2¹¹ = 644489323 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644491321) 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, 107415226 + ... + 107415231.

It is an arithmetic number, because the mean of its divisors is an integer number (214830458).

Almost surely, 2^644491371 is an apocalyptic number.

644491371 is a deficient number, since it is larger than the sum of its proper divisors (214830461).

644491371 is a wasteful number, since it uses less digits than its factorization.

644491371 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214830460.

The product of its digits is 72576, while the sum is 39.

The square root of 644491371 is about 25386.8345998472. The cubic root of 644491371 is about 863.7850880616.

The spelling of 644491371 in words is "six hundred forty-four million, four hundred ninety-one thousand, three hundred seventy-one".