644402443 has 4 divisors (see below), whose sum is σ = 644457448. Its totient is φ = 644347440.

The previous prime is 644402413. The next prime is 644402483. The reversal of 644402443 is 344204446.

It is a happy number.

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: 344204446 = 2 ⋅172102223.

It is a cyclic number.

It is not a de Polignac number, because 644402443 - 2⁵ = 644402411 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644402413) 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, 2121 + ... + 35962.

It is an arithmetic number, because the mean of its divisors is an integer number (161114362).

Almost surely, 2^644402443 is an apocalyptic number.

644402443 is a deficient number, since it is larger than the sum of its proper divisors (55005).

644402443 is a wasteful number, since it uses less digits than its factorization.

644402443 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55004.

The product of its (nonzero) digits is 36864, while the sum is 31.

The square root of 644402443 is about 25385.0830804234. The cubic root of 644402443 is about 863.7453573959.

Adding to 644402443 its reverse (344204446), we get a palindrome (988606889).

The spelling of 644402443 in words is "six hundred forty-four million, four hundred two thousand, four hundred forty-three".