644052691 has 4 divisors (see below), whose sum is σ = 647322192. Its totient is φ = 640783192.

The previous prime is 644052679. The next prime is 644052713. The reversal of 644052691 is 196250446.

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

It is a cyclic number.

It is not a de Polignac number, because 644052691 - 2¹¹ = 644050643 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644052691.

It is not an unprimeable number, because it can be changed into a prime (644052611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1634455 + ... + 1634848.

It is an arithmetic number, because the mean of its divisors is an integer number (161830548).

Almost surely, 2^644052691 is an apocalyptic number.

644052691 is a deficient number, since it is larger than the sum of its proper divisors (3269501).

644052691 is a wasteful number, since it uses less digits than its factorization.

644052691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3269500.

The product of its (nonzero) digits is 51840, while the sum is 37.

The square root of 644052691 is about 25378.1932178002. The cubic root of 644052691 is about 863.5890620349.

The spelling of 644052691 in words is "six hundred forty-four million, fifty-two thousand, six hundred ninety-one".