19990597021 has 2 divisors, whose sum is σ = 19990597022. Its totient is φ = 19990597020.

The previous prime is 19990596971. The next prime is 19990597049. The reversal of 19990597021 is 12079509991.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16855828900 + 3134768121 = 129830^2 + 55989^2 .

It is a cyclic number.

It is not a de Polignac number, because 19990597021 - 2¹³ = 19990588829 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 19990597021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19990597321) 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, 9995298510 + 9995298511.

It is an arithmetic number, because the mean of its divisors is an integer number (9995298511).

Almost surely, 2^19990597021 is an apocalyptic number.

It is an amenable number.

19990597021 is a deficient number, since it is larger than the sum of its proper divisors (1).

19990597021 is an equidigital number, since it uses as much as digits as its factorization.

19990597021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 459270, while the sum is 52.

The spelling of 19990597021 in words is "nineteen billion, nine hundred ninety million, five hundred ninety-seven thousand, twenty-one".