66663221 has 4 divisors (see below), whose sum is σ = 66794700. Its totient is φ = 66531744.

The previous prime is 66663217. The next prime is 66663271. The reversal of 66663221 is 12236666.

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 59830225 + 6832996 = 7735^2 + 2614^2 .

It is a cyclic number.

It is not a de Polignac number, because 66663221 - 2² = 66663217 is a prime.

It is a Duffinian 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 (66663271) 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, 64976 + ... + 65993.

It is an arithmetic number, because the mean of its divisors is an integer number (16698675).

Almost surely, 2^66663221 is an apocalyptic number.

It is an amenable number.

66663221 is a deficient number, since it is larger than the sum of its proper divisors (131479).

66663221 is a wasteful number, since it uses less digits than its factorization.

66663221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 131478.

The product of its digits is 15552, while the sum is 32.

The square root of 66663221 is about 8164.7548034218. The cubic root of 66663221 is about 405.4731471710.

Adding to 66663221 its reverse (12236666), we get a palindrome (78899887).

The spelling of 66663221 in words is "sixty-six million, six hundred sixty-three thousand, two hundred twenty-one".