216501 has 4 divisors (see below), whose sum is σ = 288672. Its totient is φ = 144332.

The previous prime is 216493. The next prime is 216509. The reversal of 216501 is 105612.

216501 is nontrivially palindromic in base 14.

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 an interprime number because it is at equal distance from previous prime (216493) and next prime (216509).

It is a cyclic number.

It is not a de Polignac number, because 216501 - 2³ = 216493 is a prime.

It is a D-number.

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

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216509) 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, 36081 + ... + 36086.

It is an arithmetic number, because the mean of its divisors is an integer number (72168).

2²¹⁶⁵⁰¹ is an apocalyptic number.

It is an amenable number.

216501 is a deficient number, since it is larger than the sum of its proper divisors (72171).

216501 is an equidigital number, since it uses as much as digits as its factorization.

216501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72170.

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 216501 is about 465.2966795497. The cubic root of 216501 is about 60.0463530695.

Subtracting from 216501 its reverse (105612), we obtain a square (110889 = 333²).

It can be divided in two parts, 216 and 501, that added together give a palindrome (717).

The spelling of 216501 in words is "two hundred sixteen thousand, five hundred one".