21321321 has 12 divisors (see below), whose sum is σ = 33070032. Its totient is φ = 12183528.

The previous prime is 21321301. The next prime is 21321331. The reversal of 21321321 is 12312312.

It is not a de Polignac number, because 21321321 - 2⁷ = 21321193 is a prime.

It is a plaindrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 21321321.

It is not an unprimeable number, because it can be changed into a prime (21321301) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 72375 + ... + 72668.

It is an arithmetic number, because the mean of its divisors is an integer number (2755836).

Almost surely, 2^21321321 is an apocalyptic number.

21321321 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21321321 is a deficient number, since it is larger than the sum of its proper divisors (11748711).

21321321 is a wasteful number, since it uses less digits than its factorization.

21321321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 145060 (or 145053 counting only the distinct ones).

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

The square root of 21321321 is about 4617.5015971843. The cubic root of 21321321 is about 277.2924444246.

Adding to 21321321 its reverse (12312312), we get a palindrome (33633633).

Subtracting from 21321321 its reverse (12312312), we obtain a palindrome (9009009).

The spelling of 21321321 in words is "twenty-one million, three hundred twenty-one thousand, three hundred twenty-one".