21112212809 has 2 divisors, whose sum is σ = 21112212810. Its totient is φ = 21112212808.

The previous prime is 21112212769. The next prime is 21112212811. The reversal of 21112212809 is 90821221112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14968788409 + 6143424400 = 122347^2 + 78380^2 .

It is a cyclic number.

It is not a de Polignac number, because 21112212809 - 2⁸ = 21112212553 is a prime.

Together with 21112212811, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21112212899) 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, 10556106404 + 10556106405.

It is an arithmetic number, because the mean of its divisors is an integer number (10556106405).

Almost surely, 2^21112212809 is an apocalyptic number.

It is an amenable number.

21112212809 is a deficient number, since it is larger than the sum of its proper divisors (1).

21112212809 is an equidigital number, since it uses as much as digits as its factorization.

21112212809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1152, while the sum is 29.

The spelling of 21112212809 in words is "twenty-one billion, one hundred twelve million, two hundred twelve thousand, eight hundred nine".