6688621 has 4 divisors (see below), whose sum is σ = 6695100. Its totient is φ = 6682144.

The previous prime is 6688603. The next prime is 6688631. The reversal of 6688621 is 1268866.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 5354596 + 1334025 = 2314^2 + 1155^2 .

It is a cyclic number.

It is not a de Polignac number, because 6688621 - 2⁹ = 6688109 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6688631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1306 + ... + 3883.

It is an arithmetic number, because the mean of its divisors is an integer number (1673775).

Almost surely, 2^6688621 is an apocalyptic number.

It is an amenable number.

6688621 is a deficient number, since it is larger than the sum of its proper divisors (6479).

6688621 is a wasteful number, since it uses less digits than its factorization.

6688621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6478.

The product of its digits is 27648, while the sum is 37.

The square root of 6688621 is about 2586.2368414358. The cubic root of 6688621 is about 188.4135775905.

The spelling of 6688621 in words is "six million, six hundred eighty-eight thousand, six hundred twenty-one".