644601889 has 4 divisors (see below), whose sum is σ = 647976960. Its totient is φ = 641226820.

The previous prime is 644601883. The next prime is 644601929. The reversal of 644601889 is 988106446.

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, and also an emirpimes, since its reverse is a distinct semiprime: 988106446 = 2 ⋅494053223.

It is a cyclic number.

It is not a de Polignac number, because 644601889 - 2⁵ = 644601857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644601883) 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, 1687249 + ... + 1687630.

It is an arithmetic number, because the mean of its divisors is an integer number (161994240).

Almost surely, 2^644601889 is an apocalyptic number.

It is an amenable number.

644601889 is a deficient number, since it is larger than the sum of its proper divisors (3375071).

644601889 is a wasteful number, since it uses less digits than its factorization.

644601889 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3375070.

The product of its (nonzero) digits is 331776, while the sum is 46.

The square root of 644601889 is about 25389.0111859442. The cubic root of 644601889 is about 863.8344594721.

The spelling of 644601889 in words is "six hundred forty-four million, six hundred one thousand, eight hundred eighty-nine".