644704451 has 4 divisors (see below), whose sum is σ = 649780992. Its totient is φ = 639627912.

The previous prime is 644704441. The next prime is 644704469. The reversal of 644704451 is 154407446.

644704451 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644704451 is a prime.

It is a super-2 number, since 2×644704451² = 831287658278422802, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644704441) 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, 2538080 + ... + 2538333.

It is an arithmetic number, because the mean of its divisors is an integer number (162445248).

Almost surely, 2^644704451 is an apocalyptic number.

644704451 is a deficient number, since it is larger than the sum of its proper divisors (5076541).

644704451 is a wasteful number, since it uses less digits than its factorization.

644704451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5076540.

The product of its (nonzero) digits is 53760, while the sum is 35.

The square root of 644704451 is about 25391.0309164476. The cubic root of 644704451 is about 863.8802716718.

It can be divided in two parts, 64470 and 4451, that added together give a cube (68921 = 41³).

The spelling of 644704451 in words is "six hundred forty-four million, seven hundred four thousand, four hundred fifty-one".