81409181 has 4 divisors (see below), whose sum is σ = 93039072. Its totient is φ = 69779292.

The previous prime is 81409117. The next prime is 81409187. The reversal of 81409181 is 18190418.

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 cyclic number.

It is not a de Polignac number, because 81409181 - 2⁶ = 81409117 is a prime.

It is a super-2 number, since 2×81409181² = 13254909502181522, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81409187) 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, 5814935 + ... + 5814948.

It is an arithmetic number, because the mean of its divisors is an integer number (23259768).

Almost surely, 2^81409181 is an apocalyptic number.

It is an amenable number.

81409181 is a deficient number, since it is larger than the sum of its proper divisors (11629891).

81409181 is a wasteful number, since it uses less digits than its factorization.

81409181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11629890.

The product of its (nonzero) digits is 2304, while the sum is 32.

The square root of 81409181 is about 9022.7036413705. The cubic root of 81409181 is about 433.4022169917.

Adding to 81409181 its reverse (18190418), we get a palindrome (99599599).

The spelling of 81409181 in words is "eighty-one million, four hundred nine thousand, one hundred eighty-one".