221665312 has 72 divisors (see below), whose sum is σ = 505960560. Its totient is φ = 94786560.

The previous prime is 221665307. The next prime is 221665333. The reversal of 221665312 is 213566122.

221665312 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is an unprimeable number.

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 11 ways as a sum of consecutive naturals, for example, 100639 + ... + 102817.

It is an arithmetic number, because the mean of its divisors is an integer number (7027230).

Almost surely, 2^221665312 is an apocalyptic number.

221665312 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 221665312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (252980280).

221665312 is an abundant number, since it is smaller than the sum of its proper divisors (284295248).

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

221665312 is a wasteful number, since it uses less digits than its factorization.

221665312 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2234 (or 2209 counting only the distinct ones).

The product of its digits is 4320, while the sum is 28.

The square root of 221665312 is about 14888.4287955445. The cubic root of 221665312 is about 605.2004544877.

It can be divided in two parts, 2216 and 65312, that added together give a triangular number (67528 = T₃₆₇).

The spelling of 221665312 in words is "two hundred twenty-one million, six hundred sixty-five thousand, three hundred twelve".