21090233 has 4 divisors (see below), whose sum is σ = 21170688. Its totient is φ = 21009780.

The previous prime is 21090227. The next prime is 21090239. The reversal of 21090233 is 33209012.

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 an interprime number because it is at equal distance from previous prime (21090227) and next prime (21090239).

It is a cyclic number.

It is not a de Polignac number, because 21090233 - 2¹⁰ = 21089209 is a prime.

It is a super-3 number, since 3×21090233³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21090239) 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, 39833 + ... + 40358.

It is an arithmetic number, because the mean of its divisors is an integer number (5292672).

Almost surely, 2^21090233 is an apocalyptic number.

It is an amenable number.

21090233 is a deficient number, since it is larger than the sum of its proper divisors (80455).

21090233 is an equidigital number, since it uses as much as digits as its factorization.

21090233 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80454.

The product of its (nonzero) digits is 324, while the sum is 20.

The square root of 21090233 is about 4592.4103692941. The cubic root of 21090233 is about 276.2870054096.

Adding to 21090233 its reverse (33209012), we get a palindrome (54299245).

The spelling of 21090233 in words is "twenty-one million, ninety thousand, two hundred thirty-three".