66817 has 4 divisors (see below), whose sum is σ = 67540. Its totient is φ = 66096.

The previous prime is 66809. The next prime is 66821. The reversal of 66817 is 71866.

66817 is nontrivially palindromic in base 16.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 71866 = 2 ⋅35933.

It can be written as a sum of positive squares in 2 ways, for example, as 16641 + 50176 = 129^2 + 224^2 .

It is a cyclic number.

It is not a de Polignac number, because 66817 - 2³ = 66809 is a prime.

It is a super-2 number, since 2×66817² = 8929022978, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66877) 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, 198 + ... + 415.

It is an arithmetic number, because the mean of its divisors is an integer number (16885).

2⁶⁶⁸¹⁷ is an apocalyptic number.

It is an amenable number.

66817 is a deficient number, since it is larger than the sum of its proper divisors (723).

66817 is a wasteful number, since it uses less digits than its factorization.

66817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 722.

The product of its digits is 2016, while the sum is 28.

The square root of 66817 is about 258.4898450617. The cubic root of 66817 is about 40.5784690127.

The spelling of 66817 in words is "sixty-six thousand, eight hundred seventeen".