66217978 has 8 divisors (see below), whose sum is σ = 99558720. Its totient is φ = 33031740.

The previous prime is 66217969. The next prime is 66217997. The reversal of 66217978 is 87971266.

It is a happy number.

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

It is a super-2 number, since 2×66217978² = 8769641220816968, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 37548 + ... + 39271.

It is an arithmetic number, because the mean of its divisors is an integer number (12444840).

Almost surely, 2^66217978 is an apocalyptic number.

66217978 is a deficient number, since it is larger than the sum of its proper divisors (33340742).

66217978 is a wasteful number, since it uses less digits than its factorization.

66217978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77252.

The product of its digits is 254016, while the sum is 46.

The square root of 66217978 is about 8137.4429644699. The cubic root of 66217978 is about 404.5684128750.

The spelling of 66217978 in words is "sixty-six million, two hundred seventeen thousand, nine hundred seventy-eight".