66591 has 18 divisors (see below), whose sum is σ = 112632. Its totient is φ = 37800.

The previous prime is 66587. The next prime is 66593. The reversal of 66591 is 19566.

66591 = 18³ + 19³ + ... + 24³.

66591 is a `hidden beast` number, since 6 + 659 + 1 = 666.

It is not a de Polignac number, because 66591 - 2² = 66587 is a prime.

It is a super-2 number, since 2×66591² = 8868722562, which contains 22 as substring.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66593) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 366 + ... + 516.

2⁶⁶⁵⁹¹ is an apocalyptic number.

66591 is a deficient number, since it is larger than the sum of its proper divisors (46041).

66591 is a wasteful number, since it uses less digits than its factorization.

66591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 171 (or 161 counting only the distinct ones).

The product of its digits is 1620, while the sum is 27.

The square root of 66591 is about 258.0523202763. The cubic root of 66591 is about 40.5326668312.

Subtracting from 66591 its sum of digits (27), we obtain a square (66564 = 258²).

The spelling of 66591 in words is "sixty-six thousand, five hundred ninety-one".