81778 has 8 divisors (see below), whose sum is σ = 126720. Its totient is φ = 39540.

The previous prime is 81773. The next prime is 81799. The reversal of 81778 is 87718.

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

It is a Harshad number since it is a multiple of its sum of digits (31).

It is not an unprimeable number, because it can be changed into a prime (81773) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 598 + ... + 721.

It is an arithmetic number, because the mean of its divisors is an integer number (15840).

2⁸¹⁷⁷⁸ is an apocalyptic number.

81778 is a deficient number, since it is larger than the sum of its proper divisors (44942).

81778 is a wasteful number, since it uses less digits than its factorization.

81778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1352.

The product of its digits is 3136, while the sum is 31.

The square root of 81778 is about 285.9685297371. The cubic root of 81778 is about 43.4055731267.

The spelling of 81778 in words is "eighty-one thousand, seven hundred seventy-eight".