81912181 has 8 divisors (see below), whose sum is σ = 88659200. Its totient is φ = 75228912.

The previous prime is 81912179. The next prime is 81912209. The reversal of 81912181 is 18121918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81912181 - 2¹ = 81912179 is a prime.

It is a super-2 number, since 2×81912181² = 13419210792353522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81912121) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13245 + ... + 18418.

It is an arithmetic number, because the mean of its divisors is an integer number (11082400).

Almost surely, 2^81912181 is an apocalyptic number.

It is an amenable number.

81912181 is a deficient number, since it is larger than the sum of its proper divisors (6747019).

81912181 is a wasteful number, since it uses less digits than its factorization.

81912181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31875.

The product of its digits is 1152, while the sum is 31.

The square root of 81912181 is about 9050.5348460740. The cubic root of 81912181 is about 434.2930004868.

The spelling of 81912181 in words is "eighty-one million, nine hundred twelve thousand, one hundred eighty-one".