221720028 has 12 divisors (see below), whose sum is σ = 517346760. Its totient is φ = 73906672.

The previous prime is 221720003. The next prime is 221720033. The reversal of 221720028 is 820027122.

It is a happy number.

221720028 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 9238323 + ... + 9238346.

It is an arithmetic number, because the mean of its divisors is an integer number (43112230).

Almost surely, 2^221720028 is an apocalyptic number.

It is an amenable number.

221720028 is an abundant number, since it is smaller than the sum of its proper divisors (295626732).

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

221720028 is a wasteful number, since it uses less digits than its factorization.

221720028 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18476676 (or 18476674 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 24.

The square root of 221720028 is about 14890.2662165591. The cubic root of 221720028 is about 605.2502464068.

The spelling of 221720028 in words is "two hundred twenty-one million, seven hundred twenty thousand, twenty-eight".