191818681 has 4 divisors (see below), whose sum is σ = 191891700. Its totient is φ = 191745664.

The previous prime is 191818639. The next prime is 191818691. The reversal of 191818681 is 186818191.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 188787600 + 3031081 = 13740^2 + 1741^2 .

It is a cyclic number.

It is not a de Polignac number, because 191818681 - 2¹¹ = 191816633 is a prime.

It is a super-2 number, since 2×191818681² = 73588812761159522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (191818691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 32416 + ... + 37873.

It is an arithmetic number, because the mean of its divisors is an integer number (47972925).

Almost surely, 2^191818681 is an apocalyptic number.

It is an amenable number.

191818681 is a deficient number, since it is larger than the sum of its proper divisors (73019).

191818681 is an equidigital number, since it uses as much as digits as its factorization.

191818681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73018.

The product of its digits is 27648, while the sum is 43.

The square root of 191818681 is about 13849.8621292777. The cubic root of 191818681 is about 576.7181686696.

The spelling of 191818681 in words is "one hundred ninety-one million, eight hundred eighteen thousand, six hundred eighty-one".