21031131 has 32 divisors (see below), whose sum is σ = 32325120. Its totient is φ = 12138720.

The previous prime is 21031111. The next prime is 21031151. The reversal of 21031131 is 13113012.

It is an interprime number because it is at equal distance from previous prime (21031111) and next prime (21031151).

It is not a de Polignac number, because 21031131 - 2⁹ = 21030619 is a prime.

It is a super-2 number, since 2×21031131² = 884616942278322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21031111) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 91725 + ... + 91953.

It is an arithmetic number, because the mean of its divisors is an integer number (1010160).

Almost surely, 2^21031131 is an apocalyptic number.

21031131 is a deficient number, since it is larger than the sum of its proper divisors (11293989).

21031131 is a wasteful number, since it uses less digits than its factorization.

21031131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 288 (or 266 counting only the distinct ones).

The product of its (nonzero) digits is 18, while the sum is 12.

The square root of 21031131 is about 4585.9711076281. The cubic root of 21031131 is about 276.0286805944.

Adding to 21031131 its reverse (13113012), we get a palindrome (34144143).

The spelling of 21031131 in words is "twenty-one million, thirty-one thousand, one hundred thirty-one".