221544640 has 28 divisors (see below), whose sum is σ = 527553936. Its totient is φ = 88617728.

The previous prime is 221544613. The next prime is 221544647. The reversal of 221544640 is 46445122.

221544640 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a super-3 number, since 3×221544640³ (a number of 26 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 221544599 and 221544608.

It is not an unprimeable number, because it can be changed into a prime (221544647) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 345844 + ... + 346483.

It is an arithmetic number, because the mean of its divisors is an integer number (18841212).

Almost surely, 2^221544640 is an apocalyptic number.

221544640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

221544640 is an abundant number, since it is smaller than the sum of its proper divisors (306009296).

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

221544640 is an equidigital number, since it uses as much as digits as its factorization.

221544640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 692344 (or 692334 counting only the distinct ones).

The product of its (nonzero) digits is 7680, while the sum is 28.

The square root of 221544640 is about 14884.3757007138. The cubic root of 221544640 is about 605.0906132065.

Adding to 221544640 its reverse (46445122), we get a palindrome (267989762).

The spelling of 221544640 in words is "two hundred twenty-one million, five hundred forty-four thousand, six hundred forty".