19978250021 has 2 divisors, whose sum is σ = 19978250022. Its totient is φ = 19978250020.

The previous prime is 19978249997. The next prime is 19978250027. The reversal of 19978250021 is 12005287991.

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., 18527020996 + 1451229025 = 136114^2 + 38095^2 .

It is a cyclic number.

It is not a de Polignac number, because 19978250021 - 2¹⁴ = 19978233637 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19978250027) 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, 9989125010 + 9989125011.

It is an arithmetic number, because the mean of its divisors is an integer number (9989125011).

Almost surely, 2^19978250021 is an apocalyptic number.

It is an amenable number.

19978250021 is a deficient number, since it is larger than the sum of its proper divisors (1).

19978250021 is an equidigital number, since it uses as much as digits as its factorization.

19978250021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 90720, while the sum is 44.

The spelling of 19978250021 in words is "nineteen billion, nine hundred seventy-eight million, two hundred fifty thousand, twenty-one".