216909 has 24 divisors (see below), whose sum is σ = 391872. Its totient is φ = 112320.

The previous prime is 216901. The next prime is 216911. The reversal of 216909 is 909612.

It is a happy number.

It is not a de Polignac number, because 216909 - 2³ = 216901 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216901) 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 23 ways as a sum of consecutive naturals, for example, 537 + ... + 849.

It is an arithmetic number, because the mean of its divisors is an integer number (16328).

2²¹⁶⁹⁰⁹ is an apocalyptic number.

It is an amenable number.

216909 is a deficient number, since it is larger than the sum of its proper divisors (174963).

216909 is a wasteful number, since it uses less digits than its factorization.

216909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 337 (or 334 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 27.

The square root of 216909 is about 465.7349031370. The cubic root of 216909 is about 60.0840488748.

The spelling of 216909 in words is "two hundred sixteen thousand, nine hundred nine".