21031313021 has 4 divisors (see below), whose sum is σ = 21031772544. Its totient is φ = 21030853500.

The previous prime is 21031312997. The next prime is 21031313027. The reversal of 21031313021 is 12031313012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21031313021 - 2¹⁸ = 21031050877 is a prime.

It is a super-2 number, since 2×21031313021² (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 (21031313027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 152435 + ... + 255536.

It is an arithmetic number, because the mean of its divisors is an integer number (5257943136).

Almost surely, 2^21031313021 is an apocalyptic number.

It is an amenable number.

21031313021 is a deficient number, since it is larger than the sum of its proper divisors (459523).

21031313021 is an equidigital number, since it uses as much as digits as its factorization.

21031313021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 459522.

The product of its (nonzero) digits is 108, while the sum is 17.

Adding to 21031313021 its reverse (12031313012), we get a palindrome (33062626033).

Subtracting from 21031313021 its reverse (12031313012), we obtain a palindrome (9000000009).

The spelling of 21031313021 in words is "twenty-one billion, thirty-one million, three hundred thirteen thousand, twenty-one".