21311131 has 4 divisors (see below), whose sum is σ = 21342664. Its totient is φ = 21279600.

The previous prime is 21311123. The next prime is 21311137. The reversal of 21311131 is 13111312.

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 21311131 - 2³ = 21311123 is a prime.

It is a super-2 number, since 2×21311131² = 908328608998322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21311137) 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 3 ways as a sum of consecutive naturals, for example, 14730 + ... + 16111.

It is an arithmetic number, because the mean of its divisors is an integer number (5335666).

Almost surely, 2^21311131 is an apocalyptic number.

21311131 is a deficient number, since it is larger than the sum of its proper divisors (31533).

21311131 is an equidigital number, since it uses as much as digits as its factorization.

21311131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31532.

The product of its digits is 18, while the sum is 13.

The square root of 21311131 is about 4616.3980547609. The cubic root of 21311131 is about 277.2482623549.

Adding to 21311131 its reverse (13111312), we get a palindrome (34422443).

It can be divided in two parts, 2 and 1311131, that multiplied together give a palindrome (2622262).

The spelling of 21311131 in words is "twenty-one million, three hundred eleven thousand, one hundred thirty-one".