66978210 has 64 divisors (see below), whose sum is σ = 174037248. Its totient is φ = 16399104.

The previous prime is 66978193. The next prime is 66978217. The reversal of 66978210 is 1287966.

66978210 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×66978210² = 8972161229608200, which contains 22 as substring.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (66978217) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 102244 + ... + 102896.

It is an arithmetic number, because the mean of its divisors is an integer number (2719332).

Almost surely, 2^66978210 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66978210, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (87018624).

66978210 is an abundant number, since it is smaller than the sum of its proper divisors (107059038).

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

66978210 is a wasteful number, since it uses less digits than its factorization.

66978210 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 939.

The product of its (nonzero) digits is 36288, while the sum is 39.

The square root of 66978210 is about 8184.0216275374. The cubic root of 66978210 is about 406.1107748560.

The spelling of 66978210 in words is "sixty-six million, nine hundred seventy-eight thousand, two hundred ten".