21218000009 has 2 divisors, whose sum is σ = 21218000010. Its totient is φ = 21218000008.

The previous prime is 21217999991. The next prime is 21218000039. The reversal of 21218000009 is 90000081212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15476604025 + 5741395984 = 124405^2 + 75772^2 .

It is a cyclic number.

It is not a de Polignac number, because 21218000009 - 2²⁸ = 20949564553 is a prime.

It is not a weakly prime, because it can be changed into another prime (21218000039) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10609000004 + 10609000005.

It is an arithmetic number, because the mean of its divisors is an integer number (10609000005).

Almost surely, 2^21218000009 is an apocalyptic number.

It is an amenable number.

21218000009 is a deficient number, since it is larger than the sum of its proper divisors (1).

21218000009 is an equidigital number, since it uses as much as digits as its factorization.

21218000009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 23.

The spelling of 21218000009 in words is "twenty-one billion, two hundred eighteen million, nine", and thus it is an aban number.