81181751 has 4 divisors (see below), whose sum is σ = 92779152. Its totient is φ = 69584352.

The previous prime is 81181741. The next prime is 81181753. The reversal of 81181751 is 15718118.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81181751 - 2⁶ = 81181687 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81181753) 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, 5798690 + ... + 5798703.

It is an arithmetic number, because the mean of its divisors is an integer number (23194788).

Almost surely, 2^81181751 is an apocalyptic number.

81181751 is a deficient number, since it is larger than the sum of its proper divisors (11597401).

81181751 is a wasteful number, since it uses less digits than its factorization.

81181751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11597400.

The product of its digits is 2240, while the sum is 32.

The square root of 81181751 is about 9010.0916199559. The cubic root of 81181751 is about 432.9982470012.

Adding to 81181751 its reverse (15718118), we get a palindrome (96899869).

The spelling of 81181751 in words is "eighty-one million, one hundred eighty-one thousand, seven hundred fifty-one".