13781809 has 4 divisors (see below), whose sum is σ = 13794916. Its totient is φ = 13768704.

The previous prime is 13781777. The next prime is 13781827. The reversal of 13781809 is 90818731.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90818731 = 41 ⋅2215091.

It can be written as a sum of positive squares in 2 ways, for example, as 11751184 + 2030625 = 3428^2 + 1425^2 .

It is a cyclic number.

It is not a de Polignac number, because 13781809 - 2⁵ = 13781777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (13781839) 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, 4824 + ... + 7129.

It is an arithmetic number, because the mean of its divisors is an integer number (3448729).

Almost surely, 2^13781809 is an apocalyptic number.

It is an amenable number.

13781809 is a deficient number, since it is larger than the sum of its proper divisors (13107).

13781809 is a wasteful number, since it uses less digits than its factorization.

13781809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13106.

The product of its (nonzero) digits is 12096, while the sum is 37.

The square root of 13781809 is about 3712.3858905022. The cubic root of 13781809 is about 239.7555903044.

The spelling of 13781809 in words is "thirteen million, seven hundred eighty-one thousand, eight hundred nine".