7218178666 has 4 divisors (see below), whose sum is σ = 10827268002. Its totient is φ = 3609089332.

The previous prime is 7218178657. The next prime is 7218178691. The reversal of 7218178666 is 6668718127.

7218178666 is digitally balanced in base 5, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 6668718127 = 947 ⋅7041941.

It can be written as a sum of positive squares in only one way, i.e., 5273809641 + 1944369025 = 72621^2 + 44095^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1804544665 + ... + 1804544668.

Almost surely, 2^7218178666 is an apocalyptic number.

7218178666 is a deficient number, since it is larger than the sum of its proper divisors (3609089336).

7218178666 is a wasteful number, since it uses less digits than its factorization.

7218178666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3609089335.

The product of its digits is 1354752, while the sum is 52.

The square root of 7218178666 is about 84959.8650304954. The cubic root of 7218178666 is about 1932.6025246248.

The spelling of 7218178666 in words is "seven billion, two hundred eighteen million, one hundred seventy-eight thousand, six hundred sixty-six".