221217728 has 28 divisors (see below), whose sum is σ = 441301632. Its totient is φ = 110023680.

The previous prime is 221217701. The next prime is 221217739. The reversal of 221217728 is 827712122.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 221217694 and 221217703.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3176 + ... + 21272.

Almost surely, 2^221217728 is an apocalyptic number.

It is an amenable number.

221217728 is a deficient number, since it is larger than the sum of its proper divisors (220083904).

221217728 is a wasteful number, since it uses less digits than its factorization.

221217728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18300 (or 18290 counting only the distinct ones).

The product of its digits is 6272, while the sum is 32.

The square root of 221217728 is about 14873.3899296697. The cubic root of 221217728 is about 604.7928421276.

The spelling of 221217728 in words is "two hundred twenty-one million, two hundred seventeen thousand, seven hundred twenty-eight".