21553223 has 2 divisors, whose sum is σ = 21553224. Its totient is φ = 21553222.

The previous prime is 21553183. The next prime is 21553243. The reversal of 21553223 is 32235512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21553223 - 2²⁰ = 20504647 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21553243) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10776611 + 10776612.

It is an arithmetic number, because the mean of its divisors is an integer number (10776612).

Almost surely, 2^21553223 is an apocalyptic number.

21553223 is a deficient number, since it is larger than the sum of its proper divisors (1).

21553223 is an equidigital number, since it uses as much as digits as its factorization.

21553223 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1800, while the sum is 23.

The square root of 21553223 is about 4642.5448840049. The cubic root of 21553223 is about 278.2941480527.

Adding to 21553223 its reverse (32235512), we get a palindrome (53788735).

The spelling of 21553223 in words is "twenty-one million, five hundred fifty-three thousand, two hundred twenty-three".