221531640 has 256 divisors, whose sum is σ = 780019200. Its totient is φ = 50181120.

The previous prime is 221531627. The next prime is 221531669. The reversal of 221531640 is 46135122.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 221531640.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 3034644 + ... + 3034716.

It is an arithmetic number, because the mean of its divisors is an integer number (3046950).

Almost surely, 2^221531640 is an apocalyptic number.

221531640 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 221531640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (390009600).

221531640 is an abundant number, since it is smaller than the sum of its proper divisors (558487560).

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

221531640 is a wasteful number, since it uses less digits than its factorization.

221531640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 139 (or 113 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 221531640 is about 14883.9389947688. The cubic root of 221531640 is about 605.0787776206.

Adding to 221531640 its reverse (46135122), we get a palindrome (267666762).

The spelling of 221531640 in words is "two hundred twenty-one million, five hundred thirty-one thousand, six hundred forty".