221818981 has 12 divisors (see below), whose sum is σ = 232504992. Its totient is φ = 211575000.

The previous prime is 221818957. The next prime is 221819011. The reversal of 221818981 is 189818122.

It is not a de Polignac number, because 221818981 - 2⁹ = 221818469 is a prime.

It is a super-2 number, since 2×221818981² = 98407320663756722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221818931) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 66606 + ... + 69856.

It is an arithmetic number, because the mean of its divisors is an integer number (19375416).

Almost surely, 2^221818981 is an apocalyptic number.

It is an amenable number.

221818981 is a deficient number, since it is larger than the sum of its proper divisors (10686011).

221818981 is an equidigital number, since it uses as much as digits as its factorization.

221818981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3384 (or 3353 counting only the distinct ones).

The product of its digits is 18432, while the sum is 40.

The square root of 221818981 is about 14893.5885870397. The cubic root of 221818981 is about 605.3402734867.

The spelling of 221818981 in words is "two hundred twenty-one million, eight hundred eighteen thousand, nine hundred eighty-one".