221445540 has 72 divisors (see below), whose sum is σ = 673316280. Its totient is φ = 58911744.

The previous prime is 221445491. The next prime is 221445559. The reversal of 221445540 is 45544122.

It can be written as a sum of positive squares in 4 ways, for example, as 114447204 + 106998336 = 10698^2 + 10344^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 90412 + ... + 92828.

It is an arithmetic number, because the mean of its divisors is an integer number (9351615).

Almost surely, 2^221445540 is an apocalyptic number.

221445540 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 221445540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (336658140).

221445540 is an abundant number, since it is smaller than the sum of its proper divisors (451870740).

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

221445540 is a wasteful number, since it uses less digits than its factorization.

221445540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2941 (or 2936 counting only the distinct ones).

The product of its (nonzero) digits is 6400, while the sum is 27.

The square root of 221445540 is about 14881.0463341796. The cubic root of 221445540 is about 605.0003779339. Note that the first 3 decimals are identical.

Adding to 221445540 its reverse (45544122), we get a palindrome (266989662).

The spelling of 221445540 in words is "two hundred twenty-one million, four hundred forty-five thousand, five hundred forty".