19949509991 has 2 divisors, whose sum is σ = 19949509992. Its totient is φ = 19949509990.

The previous prime is 19949509961. The next prime is 19949510059. The reversal of 19949509991 is 19990594991.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 19949509991 - 2²⁶ = 19882401127 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19949509961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9974754995 + 9974754996.

It is an arithmetic number, because the mean of its divisors is an integer number (9974754996).

Almost surely, 2^19949509991 is an apocalyptic number.

19949509991 is a deficient number, since it is larger than the sum of its proper divisors (1).

19949509991 is an equidigital number, since it uses as much as digits as its factorization.

19949509991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10628820, while the sum is 65.

The spelling of 19949509991 in words is "nineteen billion, nine hundred forty-nine million, five hundred nine thousand, nine hundred ninety-one".