21516131 has 16 divisors (see below), whose sum is σ = 26755008. Its totient is φ = 16848000.

The previous prime is 21516127. The next prime is 21516137. The reversal of 21516131 is 13161512.

It is not a de Polignac number, because 21516131 - 2² = 21516127 is a prime.

It is a super-2 number, since 2×21516131² = 925887786418322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21516137) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8021 + ... + 10361.

It is an arithmetic number, because the mean of its divisors is an integer number (1672188).

Almost surely, 2^21516131 is an apocalyptic number.

21516131 is a deficient number, since it is larger than the sum of its proper divisors (5238877).

21516131 is a wasteful number, since it uses less digits than its factorization.

21516131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2462.

The product of its digits is 180, while the sum is 20.

The square root of 21516131 is about 4638.5483720664. The cubic root of 21516131 is about 278.1344130299.

Adding to 21516131 its reverse (13161512), we get a palindrome (34677643).

The spelling of 21516131 in words is "twenty-one million, five hundred sixteen thousand, one hundred thirty-one".