221123728 has 20 divisors (see below), whose sum is σ = 489631360. Its totient is φ = 94767264.

The previous prime is 221123723. The next prime is 221123731. The reversal of 221123728 is 827321122.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a junction number, because it is equal to n+sod(n) for n = 221123696 and 221123705.

It is not an unprimeable number, because it can be changed into a prime (221123723) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 987048 + ... + 987271.

It is an arithmetic number, because the mean of its divisors is an integer number (24481568).

Almost surely, 2^221123728 is an apocalyptic number.

221123728 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

221123728 is an abundant number, since it is smaller than the sum of its proper divisors (268507632).

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

221123728 is a wasteful number, since it uses less digits than its factorization.

221123728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1974334 (or 1974328 counting only the distinct ones).

The product of its digits is 2688, while the sum is 28.

The square root of 221123728 is about 14870.2295880057. The cubic root of 221123728 is about 604.7071669847.

The spelling of 221123728 in words is "two hundred twenty-one million, one hundred twenty-three thousand, seven hundred twenty-eight".