221621904 has 150 divisors (see below), whose sum is σ = 724691526. Its totient is φ = 63221760.

The previous prime is 221621899. The next prime is 221621927. The reversal of 221621904 is 409126122.

221621904 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 216090000 + 5531904 = 14700^2 + 2352^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 345424 + ... + 346064.

Almost surely, 2^221621904 is an apocalyptic number.

221621904 is a gapful number since it is divisible by the number (24) 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 221621904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (362345763).

221621904 is an abundant number, since it is smaller than the sum of its proper divisors (503069622).

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

221621904 is an equidigital number, since it uses as much as digits as its factorization.

221621904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 683 (or 653 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 221621904 is about 14886.9709477785. The cubic root of 221621904 is about 605.1609470939.

The spelling of 221621904 in words is "two hundred twenty-one million, six hundred twenty-one thousand, nine hundred four".