21644153231 has 4 divisors (see below), whose sum is σ = 21644449632. Its totient is φ = 21643856832.

The previous prime is 21644153191. The next prime is 21644153233. The reversal of 21644153231 is 13235144612.

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.

It is a cyclic number.

It is not a de Polignac number, because 21644153231 - 2²⁶ = 21577044367 is a prime.

It is a super-2 number, since 2×21644153231² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21644153233) 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, 47306 + ... + 213368.

It is an arithmetic number, because the mean of its divisors is an integer number (5411112408).

Almost surely, 2^21644153231 is an apocalyptic number.

21644153231 is a deficient number, since it is larger than the sum of its proper divisors (296401).

21644153231 is a wasteful number, since it uses less digits than its factorization.

21644153231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 296400.

The product of its digits is 17280, while the sum is 32.

Adding to 21644153231 its reverse (13235144612), we get a palindrome (34879297843).

The spelling of 21644153231 in words is "twenty-one billion, six hundred forty-four million, one hundred fifty-three thousand, two hundred thirty-one".