66781 has 8 divisors (see below), whose sum is σ = 78624. Its totient is φ = 55920.

The previous prime is 66763. The next prime is 66791. The reversal of 66781 is 18766.

66781 is nontrivially palindromic in base 14.

It is the 106-th star number.

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

It is a cyclic number.

It is not a de Polignac number, because 66781 - 2⁵ = 66749 is a prime.

It is a super-2 number, since 2×66781² = 8919403922, which contains 22 as substring.

66781 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66701) 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, 91 + ... + 376.

It is an arithmetic number, because the mean of its divisors is an integer number (9828).

2⁶⁶⁷⁸¹ is an apocalyptic number.

It is an amenable number.

66781 is a deficient number, since it is larger than the sum of its proper divisors (11843).

66781 is a wasteful number, since it uses less digits than its factorization.

66781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 491.

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

The square root of 66781 is about 258.4202004488. The cubic root of 66781 is about 40.5711800128.

The spelling of 66781 in words is "sixty-six thousand, seven hundred eighty-one".