644871929 has 4 divisors (see below), whose sum is σ = 694477476. Its totient is φ = 595266384.

The previous prime is 644871919. The next prime is 644871937. The reversal of 644871929 is 929178446.

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

It can be written as a sum of positive squares in 2 ways, for example, as 322741225 + 322130704 = 17965^2 + 17948^2 .

It is a cyclic number.

It is not a de Polignac number, because 644871929 - 2⁸ = 644871673 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (644871919) 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, 24802754 + ... + 24802779.

It is an arithmetic number, because the mean of its divisors is an integer number (173619369).

Almost surely, 2^644871929 is an apocalyptic number.

It is an amenable number.

644871929 is a deficient number, since it is larger than the sum of its proper divisors (49605547).

644871929 is a wasteful number, since it uses less digits than its factorization.

644871929 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49605546.

The product of its digits is 870912, while the sum is 50.

The square root of 644871929 is about 25394.3286778761. The cubic root of 644871929 is about 863.9550699837.

The spelling of 644871929 in words is "six hundred forty-four million, eight hundred seventy-one thousand, nine hundred twenty-nine".