21518933 has 2 divisors, whose sum is σ = 21518934. Its totient is φ = 21518932.

The previous prime is 21518881. The next prime is 21518947. The reversal of 21518933 is 33981512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19731364 + 1787569 = 4442^2 + 1337^2 .

It is a cyclic number.

It is not a de Polignac number, because 21518933 - 2⁸ = 21518677 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21518933.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21518033) 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 as a sum of consecutive naturals, namely, 10759466 + 10759467.

It is an arithmetic number, because the mean of its divisors is an integer number (10759467).

Almost surely, 2^21518933 is an apocalyptic number.

It is an amenable number.

21518933 is a deficient number, since it is larger than the sum of its proper divisors (1).

21518933 is an equidigital number, since it uses as much as digits as its factorization.

21518933 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6480, while the sum is 32.

The square root of 21518933 is about 4638.8503963806. The cubic root of 21518933 is about 278.1464861236.

The spelling of 21518933 in words is "twenty-one million, five hundred eighteen thousand, nine hundred thirty-three".