19819991991 has 8 divisors (see below), whose sum is σ = 26458614144. Its totient is φ = 13197348920.

The previous prime is 19819991957. The next prime is 19819992091. The reversal of 19819991991 is 19919991891.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 19819991991 - 2⁹ = 19819991479 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19819991941) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3991875 + ... + 3996836.

It is an arithmetic number, because the mean of its divisors is an integer number (3307326768).

Almost surely, 2^19819991991 is an apocalyptic number.

19819991991 is a deficient number, since it is larger than the sum of its proper divisors (6638622153).

19819991991 is an equidigital number, since it uses as much as digits as its factorization.

19819991991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7989541.

The product of its digits is 4251528, while the sum is 66.

The spelling of 19819991991 in words is "nineteen billion, eight hundred nineteen million, nine hundred ninety-one thousand, nine hundred ninety-one".