199981 has 4 divisors (see below), whose sum is σ = 206464. Its totient is φ = 193500.

The previous prime is 199967. The next prime is 199999. The reversal of 199981 is 189991.

199981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 189991 = 313 ⋅607.

It is a cyclic number.

It is not a de Polignac number, because 199981 - 2⁷ = 199853 is a prime.

It is a super-2 number, since 2×199981² = 79984800722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 199981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (199921) 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, 3195 + ... + 3256.

It is an arithmetic number, because the mean of its divisors is an integer number (51616).

2¹⁹⁹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

199981 is a deficient number, since it is larger than the sum of its proper divisors (6483).

199981 is an equidigital number, since it uses as much as digits as its factorization.

199981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6482.

The product of its digits is 5832, while the sum is 37.

The square root of 199981 is about 447.1923523496. The cubic root of 199981 is about 58.4785028277.

It can be divided in two parts, 1999 and 81, that added together give a triangular number (2080 = T₆₄).

The spelling of 199981 in words is "one hundred ninety-nine thousand, nine hundred eighty-one".