644210421 has 16 divisors (see below), whose sum is σ = 874334208. Its totient is φ = 421848000.

The previous prime is 644210417. The next prime is 644210423. The reversal of 644210421 is 124012446.

It is a happy number.

It is not a de Polignac number, because 644210421 - 2² = 644210417 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 644210391 and 644210400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644210423) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 30111 + ... + 46851.

It is an arithmetic number, because the mean of its divisors is an integer number (54645888).

Almost surely, 2^644210421 is an apocalyptic number.

It is an amenable number.

644210421 is a deficient number, since it is larger than the sum of its proper divisors (230123787).

644210421 is a wasteful number, since it uses less digits than its factorization.

644210421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16972.

The product of its (nonzero) digits is 1536, while the sum is 24.

The square root of 644210421 is about 25381.3006167927. The cubic root of 644210421 is about 863.6595546030.

Adding to 644210421 its reverse (124012446), we get a palindrome (768222867).

The spelling of 644210421 in words is "six hundred forty-four million, two hundred ten thousand, four hundred twenty-one".