21318223 has 2 divisors, whose sum is σ = 21318224. Its totient is φ = 21318222.

The previous prime is 21318211. The next prime is 21318257. The reversal of 21318223 is 32281312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21318223 - 2⁵ = 21318191 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21318194 and 21318203.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21318203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10659111 + 10659112.

It is an arithmetic number, because the mean of its divisors is an integer number (10659112).

Almost surely, 2^21318223 is an apocalyptic number.

21318223 is a deficient number, since it is larger than the sum of its proper divisors (1).

21318223 is an equidigital number, since it uses as much as digits as its factorization.

21318223 is an evil number, because the sum of its binary digits is even.

The product of its digits is 576, while the sum is 22.

The square root of 21318223 is about 4617.1661222009. The cubic root of 21318223 is about 277.2790135244.

Adding to 21318223 its reverse (32281312), we get a palindrome (53599535).

The spelling of 21318223 in words is "twenty-one million, three hundred eighteen thousand, two hundred twenty-three".