1909 has 4 divisors (see below), whose sum is σ = 2016. Its totient is φ = 1804.

The previous prime is 1907. The next prime is 1913. The reversal of 1909 is 9091.

1909 is nontrivially palindromic in base 13.

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 a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 1909 - 2¹ = 1907 is a prime.

It is a Duffinian number.

1909 is an undulating number in base 13.

It is a nialpdrome in base 15 and base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1901) 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, 19 + ... + 64.

It is an arithmetic number, because the mean of its divisors is an integer number (504).

It is a 18-hyperperfect number.

It is an amenable number.

1909 is a deficient number, since it is larger than the sum of its proper divisors (107).

1909 is an equidigital number, since it uses as much as digits as its factorization.

1909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 106.

The product of its (nonzero) digits is 81, while the sum is 19.

The square root of 1909 is about 43.6921045499. The cubic root of 1909 is about 12.4051487463.

The spelling of 1909 in words is "one thousand, nine hundred nine".