19827971521 has 2 divisors, whose sum is σ = 19827971522. Its totient is φ = 19827971520.

The previous prime is 19827971489. The next prime is 19827971543. The reversal of 19827971521 is 12517972891.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14576940225 + 5251031296 = 120735^2 + 72464^2 .

It is an emirp because it is prime and its reverse (12517972891) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19827971521 - 2⁵ = 19827971489 is a prime.

It is not a weakly prime, because it can be changed into another prime (19827971591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9913985760 + 9913985761.

It is an arithmetic number, because the mean of its divisors is an integer number (9913985761).

Almost surely, 2^19827971521 is an apocalyptic number.

It is an amenable number.

19827971521 is a deficient number, since it is larger than the sum of its proper divisors (1).

19827971521 is an equidigital number, since it uses as much as digits as its factorization.

19827971521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 635040, while the sum is 52.

The spelling of 19827971521 in words is "nineteen billion, eight hundred twenty-seven million, nine hundred seventy-one thousand, five hundred twenty-one".