644532421 has 8 divisors (see below), whose sum is σ = 730644320. Its totient is φ = 563639472.

The previous prime is 644532419. The next prime is 644532431. The reversal of 644532421 is 124235446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 644532421 - 2¹ = 644532419 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644532431) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1304475 + ... + 1304968.

It is an arithmetic number, because the mean of its divisors is an integer number (91330540).

Almost surely, 2^644532421 is an apocalyptic number.

It is an amenable number.

644532421 is a deficient number, since it is larger than the sum of its proper divisors (86111899).

644532421 is a wasteful number, since it uses less digits than its factorization.

644532421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2609475.

The product of its digits is 23040, while the sum is 31.

The square root of 644532421 is about 25387.6430768987. The cubic root of 644532421 is about 863.8034268771.

Adding to 644532421 its reverse (124235446), we get a palindrome (768767867).

The spelling of 644532421 in words is "six hundred forty-four million, five hundred thirty-two thousand, four hundred twenty-one".