21231331081 has 2 divisors, whose sum is σ = 21231331082. Its totient is φ = 21231331080.

The previous prime is 21231331039. The next prime is 21231331123. The reversal of 21231331081 is 18013313212.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (21231331039) and next prime (21231331123).

It can be written as a sum of positive squares in only one way, i.e., 19594400400 + 1636930681 = 139980^2 + 40459^2 .

It is a cyclic number.

It is not a de Polignac number, because 21231331081 - 2¹⁷ = 21231200009 is a prime.

It is a super-2 number, since 2×21231331081² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21231331021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10615665540 + 10615665541.

It is an arithmetic number, because the mean of its divisors is an integer number (10615665541).

Almost surely, 2^21231331081 is an apocalyptic number.

It is an amenable number.

21231331081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21231331081 is an equidigital number, since it uses as much as digits as its factorization.

21231331081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 25.

Adding to 21231331081 its reverse (18013313212), we get a palindrome (39244644293).

The spelling of 21231331081 in words is "twenty-one billion, two hundred thirty-one million, three hundred thirty-one thousand, eighty-one".