216251 has 4 divisors (see below), whose sum is σ = 247152. Its totient is φ = 185352.

The previous prime is 216233. The next prime is 216259. The reversal of 216251 is 152612.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-216251 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216259) 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, 15440 + ... + 15453.

It is an arithmetic number, because the mean of its divisors is an integer number (61788).

2²¹⁶²⁵¹ is an apocalyptic number.

216251 is a deficient number, since it is larger than the sum of its proper divisors (30901).

216251 is an equidigital number, since it uses as much as digits as its factorization.

216251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30900.

The product of its digits is 120, while the sum is 17.

The square root of 216251 is about 465.0279561489. The cubic root of 216251 is about 60.0232317443.

Adding to 216251 its reverse (152612), we get a palindrome (368863).

The spelling of 216251 in words is "two hundred sixteen thousand, two hundred fifty-one".