221555988 has 18 divisors (see below), whose sum is σ = 560044394. Its totient is φ = 73851984.

The previous prime is 221555959. The next prime is 221556001. The reversal of 221555988 is 889555122.

It is a happy number.

221555988 is a `hidden beast` number, since 2 + 2 + 1 + 55 + 598 + 8 = 666.

It can be written as a sum of positive squares in only one way, i.e., 214681104 + 6874884 = 14652^2 + 2622^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a super-2 number, since 2×221555988² = 98174111637312288, which contains 22 as substring.

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 an upside-down number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3077131 + ... + 3077202.

Almost surely, 2^221555988 is an apocalyptic number.

It is an amenable number.

221555988 is an abundant number, since it is smaller than the sum of its proper divisors (338488406).

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

221555988 is a wasteful number, since it uses less digits than its factorization.

221555988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6154343 (or 6154338 counting only the distinct ones).

The product of its digits is 288000, while the sum is 45.

The square root of 221555988 is about 14884.7569009373. The cubic root of 221555988 is about 605.1009443841.

The spelling of 221555988 in words is "two hundred twenty-one million, five hundred fifty-five thousand, nine hundred eighty-eight".