201819939821 has 2 divisors, whose sum is σ = 201819939822. Its totient is φ = 201819939820.

The previous prime is 201819939799. The next prime is 201819939863. The reversal of 201819939821 is 128939918102.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 139342437796 + 62477502025 = 373286^2 + 249955^2 .

It is a cyclic number.

It is not a de Polignac number, because 201819939821 - 2³⁰ = 200746197997 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (201819939721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 100909969910 + 100909969911.

It is an arithmetic number, because the mean of its divisors is an integer number (100909969911).

Almost surely, 2^201819939821 is an apocalyptic number.

It is an amenable number.

201819939821 is a deficient number, since it is larger than the sum of its proper divisors (1).

201819939821 is an equidigital number, since it uses as much as digits as its factorization.

201819939821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 559872, while the sum is 53.

The spelling of 201819939821 in words is "two hundred one billion, eight hundred nineteen million, nine hundred thirty-nine thousand, eight hundred twenty-one".