216651809 has 16 divisors (see below), whose sum is σ = 243567744. Its totient is φ = 191030400.

The previous prime is 216651797. The next prime is 216651817. The reversal of 216651809 is 908156612.

It is a de Polignac number, because none of the positive numbers 2^k-216651809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216651209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 46772 + ... + 51194.

It is an arithmetic number, because the mean of its divisors is an integer number (15222984).

Almost surely, 2^216651809 is an apocalyptic number.

It is an amenable number.

216651809 is a deficient number, since it is larger than the sum of its proper divisors (26915935).

216651809 is a wasteful number, since it uses less digits than its factorization.

216651809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4568.

The product of its (nonzero) digits is 25920, while the sum is 38.

The square root of 216651809 is about 14719.0967453849. The cubic root of 216651809 is about 600.6029207931.

The spelling of 216651809 in words is "two hundred sixteen million, six hundred fifty-one thousand, eight hundred nine".