19988618821 has 2 divisors, whose sum is σ = 19988618822. Its totient is φ = 19988618820.

The previous prime is 19988618779. The next prime is 19988618827. The reversal of 19988618821 is 12881688991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19851401025 + 137217796 = 140895^2 + 11714^2 .

It is an emirp because it is prime and its reverse (12881688991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19988618821 - 2¹¹ = 19988616773 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 19988618821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19988618827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9994309410 + 9994309411.

It is an arithmetic number, because the mean of its divisors is an integer number (9994309411).

Almost surely, 2^19988618821 is an apocalyptic number.

It is an amenable number.

19988618821 is a deficient number, since it is larger than the sum of its proper divisors (1).

19988618821 is an equidigital number, since it uses as much as digits as its factorization.

19988618821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3981312, while the sum is 61.

The spelling of 19988618821 in words is "nineteen billion, nine hundred eighty-eight million, six hundred eighteen thousand, eight hundred twenty-one".