21644231 has 12 divisors (see below), whose sum is σ = 25992000. Its totient is φ = 17952480.

The previous prime is 21644197. The next prime is 21644257. The reversal of 21644231 is 13244612.

It is not a de Polignac number, because 21644231 - 2⁶ = 21644167 is a prime.

It is a super-2 number, since 2×21644231² = 936945471162722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21644197 and 21644206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21644261) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5606 + ... + 8643.

It is an arithmetic number, because the mean of its divisors is an integer number (2166000).

Almost surely, 2^21644231 is an apocalyptic number.

21644231 is a deficient number, since it is larger than the sum of its proper divisors (4347769).

21644231 is a wasteful number, since it uses less digits than its factorization.

21644231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14294 (or 14287 counting only the distinct ones).

The product of its digits is 1152, while the sum is 23.

The square root of 21644231 is about 4652.3360798635. The cubic root of 21644231 is about 278.6852949616.

Adding to 21644231 its reverse (13244612), we get a palindrome (34888843).

The spelling of 21644231 in words is "twenty-one million, six hundred forty-four thousand, two hundred thirty-one".