21231331021 has 2 divisors, whose sum is σ = 21231331022. Its totient is φ = 21231331020.

The previous prime is 21231330971. The next prime is 21231331039. The reversal of 21231331021 is 12013313212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20067838921 + 1163492100 = 141661^2 + 34110^2 .

It is a cyclic number.

It is not a de Polignac number, because 21231331021 - 2¹⁹ = 21230806733 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21231331021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21231331081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10615665510 + 10615665511.

It is an arithmetic number, because the mean of its divisors is an integer number (10615665511).

Almost surely, 2^21231331021 is an apocalyptic number.

It is an amenable number.

21231331021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21231331021 is an equidigital number, since it uses as much as digits as its factorization.

21231331021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 216, while the sum is 19.

Adding to 21231331021 its reverse (12013313212), we get a palindrome (33244644233).

The spelling of 21231331021 in words is "twenty-one billion, two hundred thirty-one million, three hundred thirty-one thousand, twenty-one".