6621 has 4 divisors (see below), whose sum is σ = 8832. Its totient is φ = 4412.

The previous prime is 6619. The next prime is 6637. The reversal of 6621 is 1266.

6621 = 23² + 24² + ... + 31².

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 a cyclic number.

It is not a de Polignac number, because 6621 - 2¹ = 6619 is a prime.

It is a D-number.

6621 is a lucky number.

It is a plaindrome in base 14 and base 16.

It is a nialpdrome in base 10.

It is a self number, because there is not a number n which added to its sum of digits gives 6621.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 6621.

It is not an unprimeable number, because it can be changed into a prime (6661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1101 + ... + 1106.

It is an arithmetic number, because the mean of its divisors is an integer number (2208).

It is an amenable number.

6621 is a deficient number, since it is larger than the sum of its proper divisors (2211).

6621 is a wasteful number, since it uses less digits than its factorization.

6621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2210.

The product of its digits is 72, while the sum is 15.

The square root of 6621 is about 81.3695274658. The cubic root of 6621 is about 18.7776480999. Note that the first 3 decimals are identical.

Adding to 6621 its reverse (1266), we get a palindrome (7887).

The spelling of 6621 in words is "six thousand, six hundred twenty-one".