21261233 has 4 divisors (see below), whose sum is σ = 24298560. Its totient is φ = 18223908.

The previous prime is 21261217. The next prime is 21261239. The reversal of 21261233 is 33216212.

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 21261233 - 2⁴ = 21261217 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21261239) 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, 1518653 + ... + 1518666.

It is an arithmetic number, because the mean of its divisors is an integer number (6074640).

Almost surely, 2^21261233 is an apocalyptic number.

It is an amenable number.

21261233 is a deficient number, since it is larger than the sum of its proper divisors (3037327).

21261233 is an equidigital number, since it uses as much as digits as its factorization.

21261233 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3037326.

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

The square root of 21261233 is about 4610.9904575915. The cubic root of 21261233 is about 277.0317097160.

Adding to 21261233 its reverse (33216212), we get a palindrome (54477445).

The spelling of 21261233 in words is "twenty-one million, two hundred sixty-one thousand, two hundred thirty-three".