21021212031 has 4 divisors (see below), whose sum is σ = 28028282712. Its totient is φ = 14014141352.

The previous prime is 21021211987. The next prime is 21021212041. The reversal of 21021212031 is 13021212012.

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 21021212031 - 2⁷ = 21021211903 is a prime.

It is a super-2 number, since 2×21021212031² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21021212031.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021212041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3503535336 + ... + 3503535341.

It is an arithmetic number, because the mean of its divisors is an integer number (7007070678).

Almost surely, 2^21021212031 is an apocalyptic number.

21021212031 is a deficient number, since it is larger than the sum of its proper divisors (7007070681).

21021212031 is an equidigital number, since it uses as much as digits as its factorization.

21021212031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7007070680.

The product of its (nonzero) digits is 48, while the sum is 15.

Adding to 21021212031 its reverse (13021212012), we get a palindrome (34042424043).

The spelling of 21021212031 in words is "twenty-one billion, twenty-one million, two hundred twelve thousand, thirty-one".