19904195021 has 2 divisors, whose sum is σ = 19904195022. Its totient is φ = 19904195020.

The previous prime is 19904194957. The next prime is 19904195023. The reversal of 19904195021 is 12059140991.

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., 18690717796 + 1213477225 = 136714^2 + 34835^2 .

It is a cyclic number.

It is not a de Polignac number, because 19904195021 - 2⁶ = 19904194957 is a prime.

Together with 19904195023, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 19904195021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19904195023) 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, 9952097510 + 9952097511.

It is an arithmetic number, because the mean of its divisors is an integer number (9952097511).

Almost surely, 2^19904195021 is an apocalyptic number.

It is an amenable number.

19904195021 is a deficient number, since it is larger than the sum of its proper divisors (1).

19904195021 is an equidigital number, since it uses as much as digits as its factorization.

19904195021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 29160, while the sum is 41.

The spelling of 19904195021 in words is "nineteen billion, nine hundred four million, one hundred ninety-five thousand, twenty-one".