66771978 has 64 divisors (see below), whose sum is σ = 170069760. Its totient is φ = 16998912.

The previous prime is 66771973. The next prime is 66771989. The reversal of 66771978 is 87917766.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 66771978.

It is not an unprimeable number, because it can be changed into a prime (66771973) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 13726 + ... + 17942.

It is an arithmetic number, because the mean of its divisors is an integer number (2657340).

Almost surely, 2^66771978 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66771978, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (85034880).

66771978 is an abundant number, since it is smaller than the sum of its proper divisors (103297782).

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

66771978 is a wasteful number, since it uses less digits than its factorization.

66771978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4271.

The product of its digits is 889056, while the sum is 51.

The square root of 66771978 is about 8171.4122402434. The cubic root of 66771978 is about 405.6935289798.

The spelling of 66771978 in words is "sixty-six million, seven hundred seventy-one thousand, nine hundred seventy-eight".