6665621 has 4 divisors (see below), whose sum is σ = 6895500. Its totient is φ = 6435744.

The previous prime is 6665611. The next prime is 6665623. The reversal of 6665621 is 1265666.

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

It can be written as a sum of positive squares in 2 ways, for example, as 1311025 + 5354596 = 1145^2 + 2314^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6665621 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6665623) 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, 114896 + ... + 114953.

It is an arithmetic number, because the mean of its divisors is an integer number (1723875).

Almost surely, 2^6665621 is an apocalyptic number.

It is an amenable number.

6665621 is a deficient number, since it is larger than the sum of its proper divisors (229879).

6665621 is a wasteful number, since it uses less digits than its factorization.

6665621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 229878.

The product of its digits is 12960, while the sum is 32.

The square root of 6665621 is about 2581.7863970515. The cubic root of 6665621 is about 188.1973651616.

The spelling of 6665621 in words is "six million, six hundred sixty-five thousand, six hundred twenty-one".