• 109^{2} = 11881 is the smallest square that contains exactly three digits '1'.

109 has 2 divisors, whose sum is σ = 110. Its totient is φ = 108.

The previous prime is 107. The next prime is 113. The reversal of 109 is 901.

Subtracting from 109 its sum of digits (10), we obtain a palindrome (99).

109 = T_{7} + T_{8} +
T_{9}.

It is a happy number.

109 is nontrivially palindromic in base 5 and base 9.

109 is an esthetic number in base 11, because in such base its adjacent digits differ by 1.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 100 + 9 = 10^2 + 3^2 .

It is a cyclic number.

It is not a de Polignac number, because 109 - 2^{1} = 107 is a prime.

Together with 107, it forms a pair of twin primes.

It is a Chen prime.

It is an alternating number because its digits alternate between odd and even.

109 is an undulating number in base 5 and base 9.

109 is a modest number, since divided by 9 gives 1 as remainder.

It is a plaindrome in base 8, base 11, base 14 and base 16.

It is a nialpdrome in base 12, base 13 and base 15.

It is a junction number, because it is equal to *n*+sod(*n*) for *n* = 95 and 104.

It is a congruent number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a Pierpont prime, being equal to 2^{2} ⋅ 3^{3} + 1.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 54 + 55.

It is an arithmetic number, because the mean of its divisors is an integer number (55).

109 is the 9-th centered triangular number.

It is an amenable number.

109 is a deficient number, since it is larger than the sum of its proper divisors (1).

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

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

The product of its (nonzero) digits is 9, while the sum is 10.

The square root of 109 is about 10.4403065089. The cubic root of 109 is about 4.7768561810.

The spelling of 109 in words is "one hundred nine", and thus it is an aban number.

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