21312131 has 8 divisors (see below), whose sum is σ = 21771984. Its totient is φ = 20856960.

The previous prime is 21312121. The next prime is 21312149. The reversal of 21312131 is 13121312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21312131 - 2¹⁰ = 21311107 is a prime.

It is a super-2 number, since 2×21312131² = 908413855522322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21312121) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8936 + ... + 11066.

It is an arithmetic number, because the mean of its divisors is an integer number (2721498).

Almost surely, 2^21312131 is an apocalyptic number.

21312131 is a deficient number, since it is larger than the sum of its proper divisors (459853).

21312131 is a wasteful number, since it uses less digits than its factorization.

21312131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2341.

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

The square root of 21312131 is about 4616.5063630412. The cubic root of 21312131 is about 277.2525988043.

Adding to 21312131 its reverse (13121312), we get a palindrome (34433443).

It can be divided in two parts, 2 and 1312131, that multiplied together give a palindrome (2624262).

The spelling of 21312131 in words is "twenty-one million, three hundred twelve thousand, one hundred thirty-one".