2991001991 has 4 divisors (see below), whose sum is σ = 3041697000. Its totient is φ = 2940306984.

The previous prime is 2991001973. The next prime is 2991002009. The reversal of 2991001991 is 1991001992.

It is a happy number.

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

It is an interprime number because it is at equal distance from previous prime (2991001973) and next prime (2991002009).

It is a cyclic number.

It is not a de Polignac number, because 2991001991 - 2⁶ = 2991001927 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 (2991001921) 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, 25347416 + ... + 25347533.

It is an arithmetic number, because the mean of its divisors is an integer number (760424250).

Almost surely, 2^2991001991 is an apocalyptic number.

2991001991 is a deficient number, since it is larger than the sum of its proper divisors (50695009).

2991001991 is an equidigital number, since it uses as much as digits as its factorization.

2991001991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50695008.

The product of its (nonzero) digits is 13122, while the sum is 41.

The square root of 2991001991 is about 54690.0538580828. The cubic root of 2991001991 is about 1440.8061957763.

Subtracting from 2991001991 its reverse (1991001992), we obtain a palindrome (999999999).

It can be divided in two parts, 2991001 and 991, that added together give a palindrome (2991992).

The spelling of 2991001991 in words is "two billion, nine hundred ninety-one million, one thousand, nine hundred ninety-one".