12115721 has 4 divisors (see below), whose sum is σ = 12125952. Its totient is φ = 12105492.

The previous prime is 12115693. The next prime is 12115729. The reversal of 12115721 is 12751121.

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, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12751121 = 487 ⋅26183.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-12115721 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 12115693 and 12115702.

It is not an unprimeable number, because it can be changed into a prime (12115729) 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, 3065 + ... + 5798.

It is an arithmetic number, because the mean of its divisors is an integer number (3031488).

Almost surely, 2^12115721 is an apocalyptic number.

It is an amenable number.

12115721 is a deficient number, since it is larger than the sum of its proper divisors (10231).

12115721 is an equidigital number, since it uses as much as digits as its factorization.

12115721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10230.

The product of its digits is 140, while the sum is 20.

The square root of 12115721 is about 3480.7644275360. The cubic root of 12115721 is about 229.6764259026.

Adding to 12115721 its reverse (12751121), we get a palindrome (24866842).

The spelling of 12115721 in words is "twelve million, one hundred fifteen thousand, seven hundred twenty-one".