644598861 has 4 divisors (see below), whose sum is σ = 859465152. Its totient is φ = 429732572.

The previous prime is 644598839. The next prime is 644598907. The reversal of 644598861 is 168895446.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 644598861 - 2⁶ = 644598797 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644598811) 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, 107433141 + ... + 107433146.

It is an arithmetic number, because the mean of its divisors is an integer number (214866288).

Almost surely, 2^644598861 is an apocalyptic number.

It is an amenable number.

644598861 is a deficient number, since it is larger than the sum of its proper divisors (214866291).

644598861 is a wasteful number, since it uses less digits than its factorization.

644598861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214866290.

The product of its digits is 1658880, while the sum is 51.

The square root of 644598861 is about 25388.9515537763. The cubic root of 644598861 is about 863.8331068569.

The spelling of 644598861 in words is "six hundred forty-four million, five hundred ninety-eight thousand, eight hundred sixty-one".