644465202551 has 4 divisors (see below), whose sum is σ = 666688140600. Its totient is φ = 622242264504.

The previous prime is 644465202533. The next prime is 644465202571. The reversal of 644465202551 is 155202564446.

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 644465202551 - 2⁶ = 644465202487 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644465202571) 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, 11111468981 + ... + 11111469038.

It is an arithmetic number, because the mean of its divisors is an integer number (166672035150).

Almost surely, 2^644465202551 is an apocalyptic number.

644465202551 is a deficient number, since it is larger than the sum of its proper divisors (22222938049).

644465202551 is a wasteful number, since it uses less digits than its factorization.

644465202551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22222938048.

The product of its (nonzero) digits is 1152000, while the sum is 44.

Adding to 644465202551 its reverse (155202564446), we get a palindrome (799667766997).

The spelling of 644465202551 in words is "six hundred forty-four billion, four hundred sixty-five million, two hundred two thousand, five hundred fifty-one".