216551 has 2 divisors, whose sum is σ = 216552. Its totient is φ = 216550.

The previous prime is 216523. The next prime is 216553. The reversal of 216551 is 155612.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-216551 is a prime.

Together with 216553, it forms a pair of twin primes.

It is a Chen prime.

It is an Ulam number.

It is equal to p₁₉₃₂₅ and since 216551 and 19325 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216553) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108275 + 108276.

It is an arithmetic number, because the mean of its divisors is an integer number (108276).

2²¹⁶⁵⁵¹ is an apocalyptic number.

216551 is a deficient number, since it is larger than the sum of its proper divisors (1).

216551 is an equidigital number, since it uses as much as digits as its factorization.

216551 is an evil number, because the sum of its binary digits is even.

The product of its digits is 300, while the sum is 20.

The square root of 216551 is about 465.3504056085. The cubic root of 216551 is about 60.0509751984.

It can be divided in two parts, 216 and 551, that added together give a palindrome (767).

The spelling of 216551 in words is "two hundred sixteen thousand, five hundred fifty-one".