216661666 has 16 divisors (see below), whose sum is σ = 361283328. Its totient is φ = 96771600.

The previous prime is 216661661. The next prime is 216661667. The reversal of 216661666 is 666166612.

216661666 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is not an unprimeable number, because it can be changed into a prime (216661661) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 133600 + ... + 135211.

It is an arithmetic number, because the mean of its divisors is an integer number (22580208).

Almost surely, 2^216661666 is an apocalyptic number.

216661666 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

216661666 is a deficient number, since it is larger than the sum of its proper divisors (144621662).

216661666 is a wasteful number, since it uses less digits than its factorization.

216661666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 268857.

The product of its digits is 93312, while the sum is 40.

The square root of 216661666 is about 14719.4315786990. The cubic root of 216661666 is about 600.6120291919.

It can be divided in two parts, 21666 and 1666, that added together give a palindrome (23332).

The spelling of 216661666 in words is "two hundred sixteen million, six hundred sixty-one thousand, six hundred sixty-six".