666221216 has 12 divisors (see below), whose sum is σ = 1311623082. Its totient is φ = 333110592.

The previous prime is 666221209. The next prime is 666221249. The reversal of 666221216 is 612122666.

It can be written as a sum of positive squares in only one way, i.e., 345811216 + 320410000 = 18596^2 + 17900^2 .

It is a Harshad number since it is a multiple of its sum of digits (32), and also a Moran number because the ratio is a prime number: 20819413 = 666221216 / (6 + 6 + 6 + 2 + 2 + 1 + 2 + 1 + 6).

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10409675 + ... + 10409738.

Almost surely, 2^666221216 is an apocalyptic number.

It is an amenable number.

666221216 is a deficient number, since it is larger than the sum of its proper divisors (645401866).

666221216 is a wasteful number, since it uses less digits than its factorization.

666221216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20819423 (or 20819415 counting only the distinct ones).

The product of its digits is 10368, while the sum is 32.

The square root of 666221216 is about 25811.2614182260. The cubic root of 666221216 is about 873.3858528847.

The spelling of 666221216 in words is "six hundred sixty-six million, two hundred twenty-one thousand, two hundred sixteen".