221781996018 has 54 divisors (see below), whose sum is σ = 528235640751. Its totient is φ = 67200005400.

The previous prime is 221781995969. The next prime is 221781996041. The reversal of 221781996018 is 810699187122.

It is a happy number.

221781996018 is a `hidden beast` number, since 2 + 2 + 17 + 8 + 19 + 9 + 601 + 8 = 666.

It can be written as a sum of positive squares in only one way, i.e., 110890998009 + 110890998009 = 333003^2 + 333003^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=333003.

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 21973153 + ... + 21983243.

Almost surely, 2^221781996018 is an apocalyptic number.

221781996018 is an abundant number, since it is smaller than the sum of its proper divisors (306453644733).

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

221781996018 is an equidigital number, since it uses as much as digits as its factorization.

221781996018 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20212 (or 10107 counting only the distinct ones).

The product of its (nonzero) digits is 870912, while the sum is 54.

The spelling of 221781996018 in words is "two hundred twenty-one billion, seven hundred eighty-one million, nine hundred ninety-six thousand, eighteen".