1231311021 has 4 divisors (see below), whose sum is σ = 1641748032. Its totient is φ = 820874012.

The previous prime is 1231311019. The next prime is 1231311073. The reversal of 1231311021 is 1201131321.

It is a happy number.

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 1231311021 - 2¹ = 1231311019 is a prime.

It is a super-2 number, since 2×1231311021² = 3032253660872124882, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1231311091) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 205218501 + ... + 205218506.

It is an arithmetic number, because the mean of its divisors is an integer number (410437008).

Almost surely, 2^1231311021 is an apocalyptic number.

It is an amenable number.

1231311021 is a deficient number, since it is larger than the sum of its proper divisors (410437011).

1231311021 is an equidigital number, since it uses as much as digits as its factorization.

1231311021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 410437010.

The product of its (nonzero) digits is 36, while the sum is 15.

The square root of 1231311021 is about 35090.0416215199. The cubic root of 1231311021 is about 1071.8218071516.

Adding to 1231311021 its reverse (1201131321), we get a palindrome (2432442342).

The spelling of 1231311021 in words is "one billion, two hundred thirty-one million, three hundred eleven thousand, twenty-one".