10001081991 has 4 divisors (see below), whose sum is σ = 13334775992. Its totient is φ = 6667387992.

The previous prime is 10001081977. The next prime is 10001082001. The reversal of 10001081991 is 19918010001.

It is a happy number.

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

It is not a de Polignac number, because 10001081991 - 2⁷ = 10001081863 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 (10001081921) 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, 1666846996 + ... + 1666847001.

It is an arithmetic number, because the mean of its divisors is an integer number (3333693998).

Almost surely, 2^10001081991 is an apocalyptic number.

10001081991 is a deficient number, since it is larger than the sum of its proper divisors (3333694001).

10001081991 is an equidigital number, since it uses as much as digits as its factorization.

10001081991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3333694000.

The product of its (nonzero) digits is 648, while the sum is 30.

Adding to 10001081991 its reverse (19918010001), we get a palindrome (29919091992).

The spelling of 10001081991 in words is "ten billion, one million, eighty-one thousand, nine hundred ninety-one".