81801111 has 8 divisors (see below), whose sum is σ = 124649344. Its totient is φ = 46743480.

The previous prime is 81801107. The next prime is 81801143. The reversal of 81801111 is 11110818.

It is a happy number.

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

It is not a de Polignac number, because 81801111 - 2² = 81801107 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21), and also a Moran number because the ratio is a prime number: 3895291 = 81801111 / (8 + 1 + 8 + 0 + 1 + 1 + 1 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81801211) 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, 1947625 + ... + 1947666.

It is an arithmetic number, because the mean of its divisors is an integer number (15581168).

Almost surely, 2^81801111 is an apocalyptic number.

81801111 is a deficient number, since it is larger than the sum of its proper divisors (42848233).

81801111 is a wasteful number, since it uses less digits than its factorization.

81801111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3895301.

The product of its (nonzero) digits is 64, while the sum is 21.

The square root of 81801111 is about 9044.3966631280. The cubic root of 81801111 is about 434.0966164166.

Adding to 81801111 its reverse (11110818), we get a palindrome (92911929).

The spelling of 81801111 in words is "eighty-one million, eight hundred one thousand, one hundred eleven".