6666621 has 16 divisors (see below), whose sum is σ = 9778944. Its totient is φ = 4014144.

The previous prime is 6666617. The next prime is 6666679. The reversal of 6666621 is 1266666.

It is not a de Polignac number, because 6666621 - 2² = 6666617 is a prime.

6666621 is a lucky number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6626621) 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, 15 + ... + 3651.

It is an arithmetic number, because the mean of its divisors is an integer number (611184).

Almost surely, 2^6666621 is an apocalyptic number.

It is an amenable number.

6666621 is a deficient number, since it is larger than the sum of its proper divisors (3112323).

6666621 is a wasteful number, since it uses less digits than its factorization.

6666621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3700.

The product of its digits is 15552, while the sum is 33.

The square root of 6666621 is about 2581.9800541445. The cubic root of 6666621 is about 188.2067760354.

The spelling of 6666621 in words is "six million, six hundred sixty-six thousand, six hundred twenty-one".