21211111309 has 2 divisors, whose sum is σ = 21211111310. Its totient is φ = 21211111308.

The previous prime is 21211111279. The next prime is 21211111319. The reversal of 21211111309 is 90311111212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16014143209 + 5196968100 = 126547^2 + 72090^2 .

It is a cyclic number.

It is not a de Polignac number, because 21211111309 - 2²⁵ = 21177556877 is a prime.

It is a super-2 number, since 2×21211111309² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21211111309.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21211111319) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605555654 + 10605555655.

It is an arithmetic number, because the mean of its divisors is an integer number (10605555655).

Almost surely, 2^21211111309 is an apocalyptic number.

It is an amenable number.

21211111309 is a deficient number, since it is larger than the sum of its proper divisors (1).

21211111309 is an equidigital number, since it uses as much as digits as its factorization.

21211111309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 108, while the sum is 22.

The spelling of 21211111309 in words is "twenty-one billion, two hundred eleven million, one hundred eleven thousand, three hundred nine".