21211302209 has 2 divisors, whose sum is σ = 21211302210. Its totient is φ = 21211302208.

The previous prime is 21211302187. The next prime is 21211302269. The reversal of 21211302209 is 90220311212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17197699600 + 4013602609 = 131140^2 + 63353^2 .

It is a cyclic number.

It is not a de Polignac number, because 21211302209 - 2²⁴ = 21194524993 is a prime.

It is not a weakly prime, because it can be changed into another prime (21211302269) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605651104 + 10605651105.

It is an arithmetic number, because the mean of its divisors is an integer number (10605651105).

Almost surely, 2^21211302209 is an apocalyptic number.

It is an amenable number.

21211302209 is a deficient number, since it is larger than the sum of its proper divisors (1).

21211302209 is an equidigital number, since it uses as much as digits as its factorization.

21211302209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 432, while the sum is 23.

The spelling of 21211302209 in words is "twenty-one billion, two hundred eleven million, three hundred two thousand, two hundred nine".