21121110209 has 2 divisors, whose sum is σ = 21121110210. Its totient is φ = 21121110208.

The previous prime is 21121110173. The next prime is 21121110211. The reversal of 21121110209 is 90201112112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15582029584 + 5539080625 = 124828^2 + 74425^2 .

It is a cyclic number.

It is not a de Polignac number, because 21121110209 - 2¹² = 21121106113 is a prime.

It is a super-2 number, since 2×21121110209² (a number of 21 digits) contains 22 as substring.

Together with 21121110211, 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 (21121112209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10560555104 + 10560555105.

It is an arithmetic number, because the mean of its divisors is an integer number (10560555105).

Almost surely, 2^21121110209 is an apocalyptic number.

It is an amenable number.

21121110209 is a deficient number, since it is larger than the sum of its proper divisors (1).

21121110209 is an equidigital number, since it uses as much as digits as its factorization.

21121110209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72, while the sum is 20.

The spelling of 21121110209 in words is "twenty-one billion, one hundred twenty-one million, one hundred ten thousand, two hundred nine".