18103781 has 4 divisors (see below), whose sum is σ = 18351852. Its totient is φ = 17855712.

The previous prime is 18103769. The next prime is 18103819. The reversal of 18103781 is 18730181.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18730181 = 19 ⋅985799.

It can be written as a sum of positive squares in 2 ways, for example, as 6604900 + 11498881 = 2570^2 + 3391^2 .

It is a cyclic number.

It is not a de Polignac number, because 18103781 - 2⁶ = 18103717 is a prime.

It is a super-2 number, since 2×18103781² = 655493772991922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18103741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 123926 + ... + 124071.

It is an arithmetic number, because the mean of its divisors is an integer number (4587963).

Almost surely, 2^18103781 is an apocalyptic number.

It is an amenable number.

18103781 is a deficient number, since it is larger than the sum of its proper divisors (248071).

18103781 is an equidigital number, since it uses as much as digits as its factorization.

18103781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 248070.

The product of its (nonzero) digits is 1344, while the sum is 29.

The square root of 18103781 is about 4254.8538165253. The cubic root of 18103781 is about 262.5768470397.

The spelling of 18103781 in words is "eighteen million, one hundred three thousand, seven hundred eighty-one".