61666 has 8 divisors (see below), whose sum is σ = 100944. Its totient is φ = 28020.

The previous prime is 61657. The next prime is 61667. The reversal of 61666 is 66616.

61666 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a self number, because there is not a number n which added to its sum of digits gives 61666.

It is not an unprimeable number, because it can be changed into a prime (61667) by changing a digit.

61666 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1380 + ... + 1423.

It is an arithmetic number, because the mean of its divisors is an integer number (12618).

2⁶¹⁶⁶⁶ is an apocalyptic number.

61666 is a deficient number, since it is larger than the sum of its proper divisors (39278).

61666 is a wasteful number, since it uses less digits than its factorization.

61666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2816.

The product of its digits is 1296, while the sum is 25.

The square root of 61666 is about 248.3263981135. The cubic root of 61666 is about 39.5077162728.

Subtracting 61666 from its reverse (66616), we obtain a triangular number (4950 = T₉₉).

It can be divided in two parts, 61 and 666, that added together give a palindrome (727).

The spelling of 61666 in words is "sixty-one thousand, six hundred sixty-six".