21231131 has 4 divisors (see below), whose sum is σ = 21263352. Its totient is φ = 21198912.

The previous prime is 21231107. The next prime is 21231143. The reversal of 21231131 is 13113212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21231131 is a prime.

It is a super-2 number, since 2×21231131² = 901521847078322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21231631) 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, 15101 + ... + 16446.

It is an arithmetic number, because the mean of its divisors is an integer number (5315838).

Almost surely, 2^21231131 is an apocalyptic number.

21231131 is a deficient number, since it is larger than the sum of its proper divisors (32221).

21231131 is an equidigital number, since it uses as much as digits as its factorization.

21231131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32220.

The product of its digits is 36, while the sum is 14.

The square root of 21231131 is about 4607.7251437125. The cubic root of 21231131 is about 276.9009059628.

Adding to 21231131 its reverse (13113212), we get a palindrome (34344343).

It can be divided in two parts, 21231 and 131, that multiplied together give a triangular number (2781261 = T₂₃₅₈).

The spelling of 21231131 in words is "twenty-one million, two hundred thirty-one thousand, one hundred thirty-one".