21122120209 has 2 divisors, whose sum is σ = 21122120210. Its totient is φ = 21122120208.

The previous prime is 21122120207. The next prime is 21122120231. The reversal of 21122120209 is 90202122112.

It is an a-pointer prime, because the next prime (21122120231) can be obtained adding 21122120209 to its sum of digits (22).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14616084609 + 6506035600 = 120897^2 + 80660^2 .

It is a cyclic number.

It is not a de Polignac number, because 21122120209 - 2¹ = 21122120207 is a prime.

It is a super-2 number, since 2×21122120209² (a number of 21 digits) contains 22 as substring.

Together with 21122120207, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21122120209.

It is not a weakly prime, because it can be changed into another prime (21122120207) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561060104 + 10561060105.

It is an arithmetic number, because the mean of its divisors is an integer number (10561060105).

Almost surely, 2^21122120209 is an apocalyptic number.

It is an amenable number.

21122120209 is a deficient number, since it is larger than the sum of its proper divisors (1).

21122120209 is an equidigital number, since it uses as much as digits as its factorization.

21122120209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 288, while the sum is 22.

The spelling of 21122120209 in words is "twenty-one billion, one hundred twenty-two million, one hundred twenty thousand, two hundred nine".