21216229 has 4 divisors (see below), whose sum is σ = 21733740. Its totient is φ = 20698720.

The previous prime is 21216203. The next prime is 21216241. The reversal of 21216229 is 92261212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3323329 + 17892900 = 1823^2 + 4230^2 .

It is a cyclic number.

It is not a de Polignac number, because 21216229 - 2¹³ = 21208037 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21216529) 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, 258694 + ... + 258775.

It is an arithmetic number, because the mean of its divisors is an integer number (5433435).

Almost surely, 2^21216229 is an apocalyptic number.

It is an amenable number.

21216229 is a deficient number, since it is larger than the sum of its proper divisors (517511).

21216229 is an equidigital number, since it uses as much as digits as its factorization.

21216229 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 517510.

The product of its digits is 864, while the sum is 25.

The square root of 21216229 is about 4606.1077929202. The cubic root of 21216229 is about 276.8361057864.

The spelling of 21216229 in words is "twenty-one million, two hundred sixteen thousand, two hundred twenty-nine".