21115121 has 4 divisors (see below), whose sum is σ = 21164544. Its totient is φ = 21065700.

The previous prime is 21115093. The next prime is 21115141. The reversal of 21115121 is 12151112.

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 21115121 - 2¹⁰ = 21114097 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21115096 and 21115105.

It is not an unprimeable number, because it can be changed into a prime (21115141) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24065 + ... + 24926.

It is an arithmetic number, because the mean of its divisors is an integer number (5291136).

Almost surely, 2^21115121 is an apocalyptic number.

It is an amenable number.

21115121 is a deficient number, since it is larger than the sum of its proper divisors (49423).

21115121 is an equidigital number, since it uses as much as digits as its factorization.

21115121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49422.

The product of its digits is 20, while the sum is 14.

The square root of 21115121 is about 4595.1192585177. The cubic root of 21115121 is about 276.3956422361.

Adding to 21115121 its reverse (12151112), we get a palindrome (33266233).

The spelling of 21115121 in words is "twenty-one million, one hundred fifteen thousand, one hundred twenty-one".