6661221 has 16 divisors (see below), whose sum is σ = 10425984. Its totient is φ = 3703104.

The previous prime is 6661217. The next prime is 6661223. The reversal of 6661221 is 1221666.

It is not a de Polignac number, because 6661221 - 2² = 6661217 is a prime.

6661221 is a modest number, since divided by 1221 gives 666 as remainder.

It is a junction number, because it is equal to n+sod(n) for n = 6661191 and 6661200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6661223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3510 + ... + 5063.

It is an arithmetic number, because the mean of its divisors is an integer number (651624).

Almost surely, 2^6661221 is an apocalyptic number.

It is an amenable number.

6661221 is a deficient number, since it is larger than the sum of its proper divisors (3764763).

6661221 is a wasteful number, since it uses less digits than its factorization.

6661221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8620.

The product of its digits is 864, while the sum is 24.

The square root of 6661221 is about 2580.9341332161. The cubic root of 6661221 is about 188.1559461312.

Adding to 6661221 its reverse (1221666), we get a palindrome (7882887).

The spelling of 6661221 in words is "six million, six hundred sixty-one thousand, two hundred twenty-one".