19501019981 has 2 divisors, whose sum is σ = 19501019982. Its totient is φ = 19501019980.

The previous prime is 19501019977. The next prime is 19501020001. The reversal of 19501019981 is 18991010591.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15641504356 + 3859515625 = 125066^2 + 62125^2 .

It is a cyclic number.

It is not a de Polignac number, because 19501019981 - 2² = 19501019977 is a prime.

It is a super-2 number, since 2×19501019981² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19501019281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9750509990 + 9750509991.

It is an arithmetic number, because the mean of its divisors is an integer number (9750509991).

Almost surely, 2^19501019981 is an apocalyptic number.

It is an amenable number.

19501019981 is a deficient number, since it is larger than the sum of its proper divisors (1).

19501019981 is an equidigital number, since it uses as much as digits as its factorization.

19501019981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 29160, while the sum is 44.

The spelling of 19501019981 in words is "nineteen billion, five hundred one million, nineteen thousand, nine hundred eighty-one".