66999978 has 12 divisors (see below), whose sum is σ = 145166658. Its totient is φ = 22333320.

The previous prime is 66999953. The next prime is 66999983. The reversal of 66999978 is 87999966.

It can be written as a sum of positive squares in only one way, i.e., 53626329 + 13373649 = 7323^2 + 3657^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1861093 + ... + 1861128.

Almost surely, 2^66999978 is an apocalyptic number.

66999978 is an abundant number, since it is smaller than the sum of its proper divisors (78166680).

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

66999978 is a wasteful number, since it uses less digits than its factorization.

66999978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3722229 (or 3722226 counting only the distinct ones).

The product of its digits is 13226976, while the sum is 63.

The square root of 66999978 is about 8185.3514280085. The cubic root of 66999978 is about 406.1547655898.

The spelling of 66999978 in words is "sixty-six million, nine hundred ninety-nine thousand, nine hundred seventy-eight".