21216233 has 4 divisors (see below), whose sum is σ = 21232128. Its totient is φ = 21200340.

The previous prime is 21216203. The next prime is 21216241. The reversal of 21216233 is 33261212.

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 21216233 - 2⁸ = 21215977 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21216203) 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, 5741 + ... + 8682.

It is an arithmetic number, because the mean of its divisors is an integer number (5308032).

Almost surely, 2^21216233 is an apocalyptic number.

It is an amenable number.

21216233 is a deficient number, since it is larger than the sum of its proper divisors (15895).

21216233 is a wasteful number, since it uses less digits than its factorization.

21216233 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15894.

The product of its digits is 432, while the sum is 20.

The square root of 21216233 is about 4606.1082271262. The cubic root of 21216233 is about 276.8361231841.

Adding to 21216233 its reverse (33261212), we get a palindrome (54477445).

The spelling of 21216233 in words is "twenty-one million, two hundred sixteen thousand, two hundred thirty-three".