21523131 has 32 divisors (see below), whose sum is σ = 36664320. Its totient is φ = 12223872.

The previous prime is 21523093. The next prime is 21523171. The reversal of 21523131 is 13132512.

It is not a de Polignac number, because 21523131 - 2⁹ = 21522619 is a prime.

It is a super-2 number, since 2×21523131² = 926490336086322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21523171) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 49491 + ... + 49923.

It is an arithmetic number, because the mean of its divisors is an integer number (1145760).

Almost surely, 2^21523131 is an apocalyptic number.

21523131 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21523131 is a deficient number, since it is larger than the sum of its proper divisors (15141189).

21523131 is a wasteful number, since it uses less digits than its factorization.

21523131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 712 (or 706 counting only the distinct ones).

The product of its digits is 180, while the sum is 18.

The square root of 21523131 is about 4639.3028571112. The cubic root of 21523131 is about 278.1645722593.

Adding to 21523131 its reverse (13132512), we get a palindrome (34655643).

The spelling of 21523131 in words is "twenty-one million, five hundred twenty-three thousand, one hundred thirty-one".