1231215121 has 4 divisors (see below), whose sum is σ = 1238768752. Its totient is φ = 1223661492.

The previous prime is 1231215109. The next prime is 1231215133. The reversal of 1231215121 is 1215121321.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1215121321 = 13553 ⋅89657.

It is an interprime number because it is at equal distance from previous prime (1231215109) and next prime (1231215133).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1231215121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1231215151) 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, 3776571 + ... + 3776896.

It is an arithmetic number, because the mean of its divisors is an integer number (309692188).

Almost surely, 2^1231215121 is an apocalyptic number.

It is an amenable number.

1231215121 is a deficient number, since it is larger than the sum of its proper divisors (7553631).

1231215121 is an equidigital number, since it uses as much as digits as its factorization.

1231215121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7553630.

The product of its digits is 120, while the sum is 19.

The square root of 1231215121 is about 35088.6751103543. The cubic root of 1231215121 is about 1071.7939803398.

Adding to 1231215121 its reverse (1215121321), we get a palindrome (2446336442).

The spelling of 1231215121 in words is "one billion, two hundred thirty-one million, two hundred fifteen thousand, one hundred twenty-one".