644343891 has 32 divisors (see below), whose sum is σ = 891072000. Its totient is φ = 413994240.

The previous prime is 644343881. The next prime is 644343893. The reversal of 644343891 is 198343446.

It is not a de Polignac number, because 644343891 - 2⁵ = 644343859 is a prime.

It is not an unprimeable number, because it can be changed into a prime (644343893) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3237810 + ... + 3238008.

It is an arithmetic number, because the mean of its divisors is an integer number (27846000).

Almost surely, 2^644343891 is an apocalyptic number.

644343891 is a deficient number, since it is larger than the sum of its proper divisors (246728109).

644343891 is a wasteful number, since it uses less digits than its factorization.

644343891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 539.

The product of its digits is 248832, while the sum is 42.

The square root of 644343891 is about 25383.9297785036. The cubic root of 644343891 is about 863.7191959236.

The spelling of 644343891 in words is "six hundred forty-four million, three hundred forty-three thousand, eight hundred ninety-one".