81751 has 4 divisors (see below), whose sum is σ = 84600. Its totient is φ = 78904.

The previous prime is 81749. The next prime is 81761. The reversal of 81751 is 15718.

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 81751 - 2¹ = 81749 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 (81701) 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, 1381 + ... + 1438.

It is an arithmetic number, because the mean of its divisors is an integer number (21150).

2⁸¹⁷⁵¹ is an apocalyptic number.

81751 is a deficient number, since it is larger than the sum of its proper divisors (2849).

81751 is a wasteful number, since it uses less digits than its factorization.

81751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2848.

The product of its digits is 280, while the sum is 22.

The square root of 81751 is about 285.9213178481. The cubic root of 81751 is about 43.4007956419.

It can be divided in two parts, 817 and 51, that added together give a palindrome (868).

The spelling of 81751 in words is "eighty-one thousand, seven hundred fifty-one".