18197681 has 4 divisors (see below), whose sum is σ = 18207012. Its totient is φ = 18188352.

The previous prime is 18197671. The next prime is 18197693. The reversal of 18197681 is 18679181.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 4389025 + 13808656 = 2095^2 + 3716^2 .

It is a cyclic number.

It is not a de Polignac number, because 18197681 - 2¹⁸ = 17935537 is a prime.

It is a super-2 number, since 2×18197681² = 662311187555522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18197671) 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, 500 + ... + 6053.

It is an arithmetic number, because the mean of its divisors is an integer number (4551753).

Almost surely, 2^18197681 is an apocalyptic number.

It is an amenable number.

18197681 is a deficient number, since it is larger than the sum of its proper divisors (9331).

18197681 is an equidigital number, since it uses as much as digits as its factorization.

18197681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9330.

The product of its digits is 24192, while the sum is 41.

The square root of 18197681 is about 4265.8740018899. The cubic root of 18197681 is about 263.0300389289.

The spelling of 18197681 in words is "eighteen million, one hundred ninety-seven thousand, six hundred eighty-one".