206308820021 has 2 divisors, whose sum is σ = 206308820022. Its totient is φ = 206308820020.

The previous prime is 206308819943. The next prime is 206308820027. The reversal of 206308820021 is 120028803602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 187618922500 + 18689897521 = 433150^2 + 136711^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-206308820021 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 206308820021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (206308820027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 103154410010 + 103154410011.

It is an arithmetic number, because the mean of its divisors is an integer number (103154410011).

Almost surely, 2^206308820021 is an apocalyptic number.

It is an amenable number.

206308820021 is a deficient number, since it is larger than the sum of its proper divisors (1).

206308820021 is an equidigital number, since it uses as much as digits as its factorization.

206308820021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9216, while the sum is 32.

The spelling of 206308820021 in words is "two hundred six billion, three hundred eight million, eight hundred twenty thousand, twenty-one".