221665212 has 72 divisors (see below), whose sum is σ = 588478800. Its totient is φ = 70253568.

The previous prime is 221665177. The next prime is 221665217. The reversal of 221665212 is 212566122.

221665212 is a `hidden beast` number, since 2 + 2 + 1 + 6 + 652 + 1 + 2 = 666.

It is a super-2 number, since 2×221665212² = 98270932422009888, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221665217) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 68364 + ... + 71532.

Almost surely, 2^221665212 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 221665212, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (294239400).

221665212 is an abundant number, since it is smaller than the sum of its proper divisors (366813588).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

221665212 is a wasteful number, since it uses less digits than its factorization.

221665212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3275 (or 3270 counting only the distinct ones).

The product of its digits is 2880, while the sum is 27.

The square root of 221665212 is about 14888.4254372314. The cubic root of 221665212 is about 605.2003634796.

The spelling of 221665212 in words is "two hundred twenty-one million, six hundred sixty-five thousand, two hundred twelve".