644928899 has 4 divisors (see below), whose sum is σ = 644989800. Its totient is φ = 644868000.

The previous prime is 644928887. The next prime is 644928917. The reversal of 644928899 is 998829446.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 998829446 = 2 ⋅499414723.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644928899 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644928829) 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, 9977 + ... + 37274.

It is an arithmetic number, because the mean of its divisors is an integer number (161247450).

Almost surely, 2^644928899 is an apocalyptic number.

644928899 is a deficient number, since it is larger than the sum of its proper divisors (60901).

644928899 is a wasteful number, since it uses less digits than its factorization.

644928899 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60900.

The product of its digits is 8957952, while the sum is 59.

The square root of 644928899 is about 25395.4503602515. The cubic root of 644928899 is about 863.9805107308.

The spelling of 644928899 in words is "six hundred forty-four million, nine hundred twenty-eight thousand, eight hundred ninety-nine".