221840 has 40 divisors (see below), whose sum is σ = 535680. Its totient is φ = 85376.

The previous prime is 221831. The next prime is 221849. The reversal of 221840 is 48122.

It is a Cunningham number, because it is equal to 471²-1.

It is an interprime number because it is at equal distance from previous prime (221831) and next prime (221849).

It is a tau number, because it is divible by the number of its divisors (40).

It is not an unprimeable number, because it can be changed into a prime (221849) by changing a digit.

221840 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3731 + ... + 3789.

It is an arithmetic number, because the mean of its divisors is an integer number (13392).

2²²¹⁸⁴⁰ is an apocalyptic number.

221840 is a gapful number since it is divisible by the number (20) 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 221840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (267840).

221840 is an abundant number, since it is smaller than the sum of its proper divisors (313840).

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

221840 is a wasteful number, since it uses less digits than its factorization.

221840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 119 (or 113 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 17.

The square root of 221840 is about 470.9989384277. The cubic root of 221840 is about 60.5359393049.

Adding to 221840 its reverse (48122), we get a palindrome (269962).

The spelling of 221840 in words is "two hundred twenty-one thousand, eight hundred forty".