21323131 has 4 divisors (see below), whose sum is σ = 21684600. Its totient is φ = 20961664.

The previous prime is 21323129. The next prime is 21323153. The reversal of 21323131 is 13132312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21323131 - 2¹ = 21323129 is a prime.

It is a super-2 number, since 2×21323131² = 909351831286322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21323161) 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, 180646 + ... + 180763.

It is an arithmetic number, because the mean of its divisors is an integer number (5421150).

Almost surely, 2^21323131 is an apocalyptic number.

21323131 is a deficient number, since it is larger than the sum of its proper divisors (361469).

21323131 is an equidigital number, since it uses as much as digits as its factorization.

21323131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 361468.

The product of its digits is 108, while the sum is 16.

The square root of 21323131 is about 4617.6975864602. The cubic root of 21323131 is about 277.3002907977.

Adding to 21323131 its reverse (13132312), we get a palindrome (34455443).

The spelling of 21323131 in words is "twenty-one million, three hundred twenty-three thousand, one hundred thirty-one".