18145781 has 4 divisors (see below), whose sum is σ = 18934752. Its totient is φ = 17356812.

The previous prime is 18145763. The next prime is 18145801. The reversal of 18145781 is 18754181.

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.

It is a de Polignac number, because none of the positive numbers 2^k-18145781 is a prime.

It is a super-2 number, since 2×18145781² = 658538736199922, 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 (18145711) 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, 394451 + ... + 394496.

It is an arithmetic number, because the mean of its divisors is an integer number (4733688).

Almost surely, 2^18145781 is an apocalyptic number.

It is an amenable number.

18145781 is a deficient number, since it is larger than the sum of its proper divisors (788971).

18145781 is an equidigital number, since it uses as much as digits as its factorization.

18145781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 788970.

The product of its digits is 8960, while the sum is 35.

The square root of 18145781 is about 4259.7864969972. The cubic root of 18145781 is about 262.7797459113.

Subtracting 18145781 from its reverse (18754181), we obtain a square (608400 = 780²).

The spelling of 18145781 in words is "eighteen million, one hundred forty-five thousand, seven hundred eighty-one".