21131131 has 4 divisors (see below), whose sum is σ = 24149872. Its totient is φ = 18112392.

The previous prime is 21131087. The next prime is 21131137. The reversal of 21131131 is 13113112.

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 21131131 - 2⁹ = 21130619 is a prime.

It is a super-2 number, since 2×21131131² = 893049394678322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21131137) 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, 1509360 + ... + 1509373.

It is an arithmetic number, because the mean of its divisors is an integer number (6037468).

Almost surely, 2^21131131 is an apocalyptic number.

21131131 is a deficient number, since it is larger than the sum of its proper divisors (3018741).

21131131 is an equidigital number, since it uses as much as digits as its factorization.

21131131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3018740.

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

The square root of 21131131 is about 4596.8609942003. The cubic root of 21131131 is about 276.4654812281.

Adding to 21131131 its reverse (13113112), we get a palindrome (34244243).

The spelling of 21131131 in words is "twenty-one million, one hundred thirty-one thousand, one hundred thirty-one".