21021321 has 4 divisors (see below), whose sum is σ = 28028432. Its totient is φ = 14014212.

The previous prime is 21021293. The next prime is 21021323. The reversal of 21021321 is 12312012.

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 not a de Polignac number, because 21021321 - 2¹⁵ = 20988553 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21021297 and 21021306.

It is not an unprimeable number, because it can be changed into a prime (21021323) 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, 3503551 + ... + 3503556.

It is an arithmetic number, because the mean of its divisors is an integer number (7007108).

Almost surely, 2^21021321 is an apocalyptic number.

It is an amenable number.

21021321 is a deficient number, since it is larger than the sum of its proper divisors (7007111).

21021321 is an equidigital number, since it uses as much as digits as its factorization.

21021321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7007110.

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 21021321 is about 4584.9014166065. The cubic root of 21021321 is about 275.9857559337.

Adding to 21021321 its reverse (12312012), we get a palindrome (33333333).

The spelling of 21021321 in words is "twenty-one million, twenty-one thousand, three hundred twenty-one".