21123312131 has 16 divisors (see below), whose sum is σ = 22097484288. Its totient is φ = 20172012000.

The previous prime is 21123312121. The next prime is 21123312163. The reversal of 21123312131 is 13121332112.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21123312131 - 2²² = 21119117827 is a prime.

It is a super-2 number, since 2×21123312131² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21123312121) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2139356 + ... + 2149206.

It is an arithmetic number, because the mean of its divisors is an integer number (1381092768).

Almost surely, 2^21123312131 is an apocalyptic number.

21123312131 is a deficient number, since it is larger than the sum of its proper divisors (974172157).

21123312131 is a wasteful number, since it uses less digits than its factorization.

21123312131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11002.

The product of its digits is 216, while the sum is 20.

Adding to 21123312131 its reverse (13121332112), we get a palindrome (34244644243).

The spelling of 21123312131 in words is "twenty-one billion, one hundred twenty-three million, three hundred twelve thousand, one hundred thirty-one".