21132121 has 4 divisors (see below), whose sum is σ = 21168000. Its totient is φ = 21096244.

The previous prime is 21132119. The next prime is 21132127. The reversal of 21132121 is 12123112.

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 21132121 - 2¹ = 21132119 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21132127) 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, 17041 + ... + 18238.

It is an arithmetic number, because the mean of its divisors is an integer number (5292000).

Almost surely, 2^21132121 is an apocalyptic number.

It is an amenable number.

21132121 is a deficient number, since it is larger than the sum of its proper divisors (35879).

21132121 is an equidigital number, since it uses as much as digits as its factorization.

21132121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35878.

The product of its digits is 24, while the sum is 13.

The square root of 21132121 is about 4596.9686751162. The cubic root of 21132121 is about 276.4697986583.

Adding to 21132121 its reverse (12123112), we get a palindrome (33255233).

Subtracting from 21132121 its reverse (12123112), we obtain a palindrome (9009009).

The spelling of 21132121 in words is "twenty-one million, one hundred thirty-two thousand, one hundred twenty-one".