21818233 has 4 divisors (see below), whose sum is σ = 21839220. Its totient is φ = 21797248.

The previous prime is 21818227. The next prime is 21818267. The reversal of 21818233 is 33281812.

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 14348944 + 7469289 = 3788^2 + 2733^2 .

It is a cyclic number.

It is not a de Polignac number, because 21818233 - 2⁵ = 21818201 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21818833) 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, 8848 + ... + 11041.

It is an arithmetic number, because the mean of its divisors is an integer number (5459805).

Almost surely, 2^21818233 is an apocalyptic number.

It is an amenable number.

21818233 is a deficient number, since it is larger than the sum of its proper divisors (20987).

21818233 is a wasteful number, since it uses less digits than its factorization.

21818233 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20986.

The product of its digits is 2304, while the sum is 28.

The square root of 21818233 is about 4670.9991436522. Note that the first 3 decimals coincide. The cubic root of 21818233 is about 279.4301036067.

The spelling of 21818233 in words is "twenty-one million, eight hundred eighteen thousand, two hundred thirty-three".