216621 has 16 divisors (see below), whose sum is σ = 328320. Its totient is φ = 141120.

The previous prime is 216617. The next prime is 216641. The reversal of 216621 is 126612.

It is a happy number.

216621 is a `hidden beast` number, since 2 + 1 + 662 + 1 = 666.

It is not a de Polignac number, because 216621 - 2² = 216617 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 216594 and 216603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216641) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1861 + ... + 1973.

It is an arithmetic number, because the mean of its divisors is an integer number (20520).

2²¹⁶⁶²¹ is an apocalyptic number.

It is an amenable number.

216621 is a deficient number, since it is larger than the sum of its proper divisors (111699).

216621 is a wasteful number, since it uses less digits than its factorization.

216621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 193 (or 187 counting only the distinct ones).

The product of its digits is 144, while the sum is 18.

The square root of 216621 is about 465.4256116717. The cubic root of 216621 is about 60.0574449837.

Subtracting from 216621 its reverse (126612), we obtain a palindrome (90009).

It can be divided in two parts, 2166 and 21, that added together give a 7-th power (2187 = 3⁷).

The spelling of 216621 in words is "two hundred sixteen thousand, six hundred twenty-one".