21120404209 has 2 divisors, whose sum is σ = 21120404210. Its totient is φ = 21120404208.

The previous prime is 21120404167. The next prime is 21120404233. The reversal of 21120404209 is 90240402112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17411594209 + 3708810000 = 131953^2 + 60900^2 .

It is a cyclic number.

It is not a de Polignac number, because 21120404209 - 2²⁹ = 20583533297 is a prime.

It is not a weakly prime, because it can be changed into another prime (21120404609) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10560202104 + 10560202105.

It is an arithmetic number, because the mean of its divisors is an integer number (10560202105).

Almost surely, 2^21120404209 is an apocalyptic number.

It is an amenable number.

21120404209 is a deficient number, since it is larger than the sum of its proper divisors (1).

21120404209 is an equidigital number, since it uses as much as digits as its factorization.

21120404209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 25.

The spelling of 21120404209 in words is "twenty-one billion, one hundred twenty million, four hundred four thousand, two hundred nine".