109981 has 4 divisors (see below), whose sum is σ = 111100. Its totient is φ = 108864.

The previous prime is 109961. The next prime is 109987. The reversal of 109981 is 189901.

109981 = 234² + 235².

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

It can be written as a sum of positive squares in 2 ways, for example, as 55225 + 54756 = 235^2 + 234^2 .

It is a cyclic number.

It is not a de Polignac number, because 109981 - 2⁹ = 109469 is a prime.

It is a super-2 number, since 2×109981² = 24191640722, which contains 22 as substring.

It is a Duffinian number.

109981 is a modest number, since divided by 981 gives 109 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (109987) 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 3 ways as a sum of consecutive naturals, for example, 396 + ... + 613.

It is an arithmetic number, because the mean of its divisors is an integer number (27775).

2¹⁰⁹⁹⁸¹ is an apocalyptic number.

109981 is the 235-th centered square number.

It is an amenable number.

109981 is a deficient number, since it is larger than the sum of its proper divisors (1119).

109981 is a wasteful number, since it uses less digits than its factorization.

109981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1118.

The product of its (nonzero) digits is 648, while the sum is 28.

The square root of 109981 is about 331.6338342208. The cubic root of 109981 is about 47.9114397155.

It can be divided in two parts, 109 and 981, that multiplied together give a square (106929 = 327²).

The spelling of 109981 in words is "one hundred nine thousand, nine hundred eighty-one".