21313221 has 16 divisors (see below), whose sum is σ = 29395584. Its totient is φ = 13725504.

The previous prime is 21313207. The next prime is 21313241. The reversal of 21313221 is 12231312.

It is not a de Polignac number, because 21313221 - 2⁷ = 21313093 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21313221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21313241) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16816 + ... + 18038.

It is an arithmetic number, because the mean of its divisors is an integer number (1837224).

Almost surely, 2^21313221 is an apocalyptic number.

It is an amenable number.

21313221 is a deficient number, since it is larger than the sum of its proper divisors (8082363).

21313221 is a wasteful number, since it uses less digits than its factorization.

21313221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1420.

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

The square root of 21313221 is about 4616.6244161725. The cubic root of 21313221 is about 277.2573253797.

Adding to 21313221 its reverse (12231312), we get a palindrome (33544533).

The spelling of 21313221 in words is "twenty-one million, three hundred thirteen thousand, two hundred twenty-one".