216391817 has 4 divisors (see below), whose sum is σ = 227780880. Its totient is φ = 205002756.

The previous prime is 216391801. The next prime is 216391837. The reversal of 216391817 is 718193612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 216391817 - 2⁴ = 216391801 is a prime.

It is a super-2 number, since 2×216391817² = 93650836929122978, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216391837) 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 3 ways as a sum of consecutive naturals, for example, 5694503 + ... + 5694540.

It is an arithmetic number, because the mean of its divisors is an integer number (56945220).

Almost surely, 2^216391817 is an apocalyptic number.

It is an amenable number.

216391817 is a deficient number, since it is larger than the sum of its proper divisors (11389063).

216391817 is a wasteful number, since it uses less digits than its factorization.

216391817 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11389062.

The product of its digits is 18144, while the sum is 38.

The square root of 216391817 is about 14710.2623022161. The cubic root of 216391817 is about 600.3625743741.

The spelling of 216391817 in words is "two hundred sixteen million, three hundred ninety-one thousand, eight hundred seventeen".