216409217 has 4 divisors (see below), whose sum is σ = 216448260. Its totient is φ = 216370176.

The previous prime is 216409199. The next prime is 216409247. The reversal of 216409217 is 712904612.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 185395456 + 31013761 = 13616^2 + 5569^2 .

It is a cyclic number.

It is not a de Polignac number, because 216409217 - 2¹⁸ = 216147073 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216409247) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9488 + ... + 22865.

It is an arithmetic number, because the mean of its divisors is an integer number (54112065).

Almost surely, 2^216409217 is an apocalyptic number.

It is an amenable number.

216409217 is a deficient number, since it is larger than the sum of its proper divisors (39043).

216409217 is an equidigital number, since it uses as much as digits as its factorization.

216409217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39042.

The product of its (nonzero) digits is 6048, while the sum is 32.

The square root of 216409217 is about 14710.8537141799. The cubic root of 216409217 is about 600.3786656000.

The spelling of 216409217 in words is "two hundred sixteen million, four hundred nine thousand, two hundred seventeen".