21321221 has 4 divisors (see below), whose sum is σ = 21774912. Its totient is φ = 20867532.

The previous prime is 21321217. The next prime is 21321263. The reversal of 21321221 is 12212312.

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.

It is a cyclic number.

It is not a de Polignac number, because 21321221 - 2² = 21321217 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21321196 and 21321205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21321121) 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, 226775 + ... + 226868.

It is an arithmetic number, because the mean of its divisors is an integer number (5443728).

Almost surely, 2^21321221 is an apocalyptic number.

It is an amenable number.

21321221 is a deficient number, since it is larger than the sum of its proper divisors (453691).

21321221 is an equidigital number, since it uses as much as digits as its factorization.

21321221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 453690.

The product of its digits is 48, while the sum is 14.

The square root of 21321221 is about 4617.4907688051. The cubic root of 21321221 is about 277.2920109104.

Adding to 21321221 its reverse (12212312), we get a palindrome (33533533).

The spelling of 21321221 in words is "twenty-one million, three hundred twenty-one thousand, two hundred twenty-one".