181213409 has 4 divisors (see below), whose sum is σ = 195152916. Its totient is φ = 167273904.

The previous prime is 181213397. The next prime is 181213411. The reversal of 181213409 is 904312181.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 904312181 = 167 ⋅5415043.

It can be written as a sum of positive squares in 2 ways, for example, as 10336225 + 170877184 = 3215^2 + 13072^2 .

It is a cyclic number.

It is not a de Polignac number, because 181213409 - 2¹⁶ = 181147873 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (181213499) 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, 6969734 + ... + 6969759.

It is an arithmetic number, because the mean of its divisors is an integer number (48788229).

Almost surely, 2^181213409 is an apocalyptic number.

It is an amenable number.

181213409 is a deficient number, since it is larger than the sum of its proper divisors (13939507).

181213409 is a wasteful number, since it uses less digits than its factorization.

181213409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13939506.

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 181213409 is about 13461.5529936185. The cubic root of 181213409 is about 565.8875121383.

The spelling of 181213409 in words is "one hundred eighty-one million, two hundred thirteen thousand, four hundred nine".