65661 has 8 divisors (see below), whose sum is σ = 89760. Its totient is φ = 42672.

The previous prime is 65657. The next prime is 65677. The reversal of 65661 is 16656.

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

It is not a de Polignac number, because 65661 - 2² = 65657 is a prime.

It is a super-2 number, since 2×65661² = 8622733842, which contains 22 as substring.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

65661 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (65651) 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 7 ways as a sum of consecutive naturals, for example, 126 + ... + 383.

It is an arithmetic number, because the mean of its divisors is an integer number (11220).

2⁶⁵⁶⁶¹ is an apocalyptic number.

It is an amenable number.

65661 is a deficient number, since it is larger than the sum of its proper divisors (24099).

65661 is a wasteful number, since it uses less digits than its factorization.

65661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 555.

The product of its digits is 1080, while the sum is 24.

The square root of 65661 is about 256.2440243206. The cubic root of 65661 is about 40.3430904761.

It can be divided in two parts, 656 and 61, that added together give a palindrome (717).

The spelling of 65661 in words is "sixty-five thousand, six hundred sixty-one".