216931 has 16 divisors (see below), whose sum is σ = 268128. Its totient is φ = 172800.

The previous prime is 216919. The next prime is 216947. The reversal of 216931 is 139612.

It is a 8-Lehmer number, since φ(216931) divides (216931-1)⁸.

It is a cyclic number.

It is not a de Polignac number, because 216931 - 2⁵ = 216899 is a prime.

It is a super-2 number, since 2×216931² = 94118117522, which contains 22 as substring.

It is a deceptive number, since it divides R₂₁₆₉₃₀.

It is a Duffinian number.

216931 is a lucky number.

It is a nialpdrome in base 15.

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 15 ways as a sum of consecutive naturals, for example, 5271 + ... + 5311.

It is an arithmetic number, because the mean of its divisors is an integer number (16758).

2²¹⁶⁹³¹ is an apocalyptic number.

216931 is a deficient number, since it is larger than the sum of its proper divisors (51197).

216931 is a wasteful number, since it uses less digits than its factorization.

216931 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 102.

The product of its digits is 324, while the sum is 22.

The square root of 216931 is about 465.7585211244. The cubic root of 216931 is about 60.0860801481.

The spelling of 216931 in words is "two hundred sixteen thousand, nine hundred thirty-one".