109991 has 8 divisors (see below), whose sum is σ = 132480. Its totient is φ = 89208.

The previous prime is 109987. The next prime is 110017. The reversal of 109991 is 199901.

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

It is not a de Polignac number, because 109991 - 2² = 109987 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 (109961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 281 + ... + 546.

It is an arithmetic number, because the mean of its divisors is an integer number (16560).

2¹⁰⁹⁹⁹¹ is an apocalyptic number.

109991 is a deficient number, since it is larger than the sum of its proper divisors (22489).

109991 is an equidigital number, since it uses as much as digits as its factorization.

109991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 853.

The product of its (nonzero) digits is 729, while the sum is 29.

The square root of 109991 is about 331.6489107475. The cubic root of 109991 is about 47.9128917841.

It can be divided in two parts, 10 and 9991, that added together give a palindrome (10001).

The spelling of 109991 in words is "one hundred nine thousand, nine hundred ninety-one".