21311020309 has 2 divisors, whose sum is σ = 21311020310.
Its totient is φ = 21311020308.
The previous prime is 21311020253. The next prime is 21311020343. The reversal of 21311020309 is 90302011312.
It is a strong prime.
It can be written as a sum of positive squares in only one way, i.e., 17629200625 + 3681819684 = 132775^2 + 60678^2
It is a cyclic number.
It is not a de Polignac number, because 21311020309 - 29 = 21311019797 is a prime.
It is a super-2 number, since 2×213110203092 (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 21311020309.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (21311020609) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (19) of ones.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10655510154 + 10655510155.
It is an arithmetic number, because the mean of its divisors is an integer number (10655510155).
Almost surely, 221311020309 is an apocalyptic number.
It is an amenable number.
21311020309 is a deficient number, since it is larger than the sum of its proper divisors (1).
21311020309 is an equidigital number, since it uses as much as digits as its factorization.
21311020309 is an odious number, because the sum of its binary digits is odd.
The product of its (nonzero) digits is 324, while the sum is 22.
The spelling of 21311020309 in words is "twenty-one billion, three hundred eleven million, twenty thousand, three hundred nine".