21323121 has 4 divisors (see below), whose sum is σ = 28430832. Its totient is φ = 14215412.

The previous prime is 21323089. The next prime is 21323129. The reversal of 21323121 is 12132312.

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 21323121 - 2⁵ = 21323089 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21323121.

It is not an unprimeable number, because it can be changed into a prime (21323129) 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, 3553851 + ... + 3553856.

It is an arithmetic number, because the mean of its divisors is an integer number (7107708).

Almost surely, 2^21323121 is an apocalyptic number.

It is an amenable number.

21323121 is a deficient number, since it is larger than the sum of its proper divisors (7107711).

21323121 is an equidigital number, since it uses as much as digits as its factorization.

21323121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7107710.

The product of its digits is 72, while the sum is 15.

The square root of 21323121 is about 4617.6965036693. The cubic root of 21323121 is about 277.3002474488.

Adding to 21323121 its reverse (12132312), we get a palindrome (33455433).

It can be divided in two parts, 2132 and 3121, that added together give a triangular number (5253 = T₁₀₂).

The spelling of 21323121 in words is "twenty-one million, three hundred twenty-three thousand, one hundred twenty-one".