66978 has 18 divisors (see below), whose sum is σ = 147537. Its totient is φ = 21960.

The previous prime is 66977. The next prime is 67003. The reversal of 66978 is 87966.

66978 is nontrivially palindromic in base 13.

It can be written as a sum of positive squares in 2 ways, for example, as 45369 + 21609 = 213^2 + 147^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=183.

It is not an unprimeable number, because it can be changed into a prime (66973) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1068 + ... + 1128.

2⁶⁶⁹⁷⁸ is an apocalyptic number.

66978 is an abundant number, since it is smaller than the sum of its proper divisors (80559).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

66978 is a wasteful number, since it uses less digits than its factorization.

66978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 130 (or 66 counting only the distinct ones).

The product of its digits is 18144, while the sum is 36.

The square root of 66978 is about 258.8010819143. The cubic root of 66978 is about 40.6110350423.

It can be divided in two parts, 669 and 78, that added together give a palindrome (747).

The spelling of 66978 in words is "sixty-six thousand, nine hundred seventy-eight".