181819409 has 2 divisors, whose sum is σ = 181819410. Its totient is φ = 181819408.

The previous prime is 181819399. The next prime is 181819459. The reversal of 181819409 is 904918181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 110838784 + 70980625 = 10528^2 + 8425^2 .

It is a cyclic number.

It is not a de Polignac number, because 181819409 - 2²⁴ = 165042193 is a prime.

It is not a weakly prime, because it can be changed into another prime (181819459) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90909704 + 90909705.

It is an arithmetic number, because the mean of its divisors is an integer number (90909705).

Almost surely, 2^181819409 is an apocalyptic number.

It is an amenable number.

181819409 is a deficient number, since it is larger than the sum of its proper divisors (1).

181819409 is an equidigital number, since it uses as much as digits as its factorization.

181819409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20736, while the sum is 41.

The square root of 181819409 is about 13484.0427543078. The cubic root of 181819409 is about 566.5176095072.

The spelling of 181819409 in words is "one hundred eighty-one million, eight hundred nineteen thousand, four hundred nine".