21131212031 has 4 divisors (see below), whose sum is σ = 21812864064. Its totient is φ = 20449560000.

The previous prime is 21131212009. The next prime is 21131212033. The reversal of 21131212031 is 13021213112.

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 21131212031 - 2⁶ = 21131211967 is a prime.

It is a super-2 number, since 2×21131212031² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21131212033) 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, 340825970 + ... + 340826031.

It is an arithmetic number, because the mean of its divisors is an integer number (5453216016).

Almost surely, 2^21131212031 is an apocalyptic number.

21131212031 is a deficient number, since it is larger than the sum of its proper divisors (681652033).

21131212031 is an equidigital number, since it uses as much as digits as its factorization.

21131212031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 681652032.

The product of its (nonzero) digits is 72, while the sum is 17.

Adding to 21131212031 its reverse (13021213112), we get a palindrome (34152425143).

The spelling of 21131212031 in words is "twenty-one billion, one hundred thirty-one million, two hundred twelve thousand, thirty-one".