19966148921 has 2 divisors, whose sum is σ = 19966148922. Its totient is φ = 19966148920.

The previous prime is 19966148863. The next prime is 19966148953. The reversal of 19966148921 is 12984166991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19540964521 + 425184400 = 139789^2 + 20620^2 .

It is a cyclic number.

It is not a de Polignac number, because 19966148921 - 2¹⁸ = 19965886777 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (19966148971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9983074460 + 9983074461.

It is an arithmetic number, because the mean of its divisors is an integer number (9983074461).

Almost surely, 2^19966148921 is an apocalyptic number.

It is an amenable number.

19966148921 is a deficient number, since it is larger than the sum of its proper divisors (1).

19966148921 is an equidigital number, since it uses as much as digits as its factorization.

19966148921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1679616, while the sum is 56.

The spelling of 19966148921 in words is "nineteen billion, nine hundred sixty-six million, one hundred forty-eight thousand, nine hundred twenty-one".