20820905009 has 2 divisors, whose sum is σ = 20820905010. Its totient is φ = 20820905008.

The previous prime is 20820904969. The next prime is 20820905011. The reversal of 20820905009 is 90050902802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18230400400 + 2590504609 = 135020^2 + 50897^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20820905009 is a prime.

Together with 20820905011, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20820905009.

It is not a weakly prime, because it can be changed into another prime (20820955009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10410452504 + 10410452505.

It is an arithmetic number, because the mean of its divisors is an integer number (10410452505).

Almost surely, 2^20820905009 is an apocalyptic number.

It is an amenable number.

20820905009 is a deficient number, since it is larger than the sum of its proper divisors (1).

20820905009 is an equidigital number, since it uses as much as digits as its factorization.

20820905009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12960, while the sum is 35.

The spelling of 20820905009 in words is "twenty billion, eight hundred twenty million, nine hundred five thousand, nine".