21540233 has 12 divisors (see below), whose sum is σ = 25447248. Its totient is φ = 18074160.

The previous prime is 21540229. The next prime is 21540247. The reversal of 21540233 is 33204512.

It is a happy number.

It is not a de Polignac number, because 21540233 - 2² = 21540229 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21540203) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3935 + ... + 7652.

It is an arithmetic number, because the mean of its divisors is an integer number (2120604).

Almost surely, 2^21540233 is an apocalyptic number.

It is an amenable number.

21540233 is a deficient number, since it is larger than the sum of its proper divisors (3907015).

21540233 is a wasteful number, since it uses less digits than its factorization.

21540233 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11624 (or 11611 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 20.

The square root of 21540233 is about 4641.1456559776. The cubic root of 21540233 is about 278.2382280714.

Adding to 21540233 its reverse (33204512), we get a palindrome (54744745).

The spelling of 21540233 in words is "twenty-one million, five hundred forty thousand, two hundred thirty-three".