231311021 has 2 divisors, whose sum is σ = 231311022. Its totient is φ = 231311020.

The previous prime is 231311009. The next prime is 231311029. The reversal of 231311021 is 120113132.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 203632900 + 27678121 = 14270^2 + 5261^2 .

It is a cyclic number.

It is not a de Polignac number, because 231311021 - 2¹⁰ = 231309997 is a prime.

It is a super-4 number, since 4×231311021⁴ (a number of 35 digits) contains 4444 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 231310987 and 231311005.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (231311029) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 115655510 + 115655511.

It is an arithmetic number, because the mean of its divisors is an integer number (115655511).

Almost surely, 2^231311021 is an apocalyptic number.

It is an amenable number.

231311021 is a deficient number, since it is larger than the sum of its proper divisors (1).

231311021 is an equidigital number, since it uses as much as digits as its factorization.

231311021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36, while the sum is 14.

The square root of 231311021 is about 15208.9125515271. The cubic root of 231311021 is about 613.8544971352.

Adding to 231311021 its reverse (120113132), we get a palindrome (351424153).

The spelling of 231311021 in words is "two hundred thirty-one million, three hundred eleven thousand, twenty-one".