11000001991 has 4 divisors (see below), whose sum is σ = 12000002184. Its totient is φ = 10000001800.

The previous prime is 11000001983. The next prime is 11000002001. The reversal of 11000001991 is 19910000011.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 11000001991 - 2³ = 11000001983 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11000001391) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 500000080 + ... + 500000101.

It is an arithmetic number, because the mean of its divisors is an integer number (3000000546).

Almost surely, 2^11000001991 is an apocalyptic number.

11000001991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

11000001991 is a deficient number, since it is larger than the sum of its proper divisors (1000000193).

11000001991 is a wasteful number, since it uses less digits than its factorization.

11000001991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1000000192.

The product of its (nonzero) digits is 81, while the sum is 22.

The spelling of 11000001991 in words is "eleven billion, one thousand, nine hundred ninety-one".