216521566 has 8 divisors (see below), whose sum is σ = 325516824. Its totient is φ = 108015960.

The previous prime is 216521531. The next prime is 216521579. The reversal of 216521566 is 665125612.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 121305 + ... + 123076.

It is an arithmetic number, because the mean of its divisors is an integer number (40689603).

Almost surely, 2^216521566 is an apocalyptic number.

216521566 is a deficient number, since it is larger than the sum of its proper divisors (108995258).

216521566 is a wasteful number, since it uses less digits than its factorization.

216521566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 244826.

The product of its digits is 21600, while the sum is 34.

The square root of 216521566 is about 14714.6717938254. The cubic root of 216521566 is about 600.4825432974.

The spelling of 216521566 in words is "two hundred sixteen million, five hundred twenty-one thousand, five hundred sixty-six".