221520345 has 32 divisors (see below), whose sum is σ = 361912320. Its totient is φ = 115677120.

The previous prime is 221520317. The next prime is 221520347. The reversal of 221520345 is 543025122.

It is not a de Polignac number, because 221520345 - 2¹² = 221516249 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (221520347) 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 31 ways as a sum of consecutive naturals, for example, 154522 + ... + 155948.

It is an arithmetic number, because the mean of its divisors is an integer number (11309760).

Almost surely, 2^221520345 is an apocalyptic number.

It is an amenable number.

221520345 is a deficient number, since it is larger than the sum of its proper divisors (140391975).

221520345 is a wasteful number, since it uses less digits than its factorization.

221520345 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1645.

The product of its (nonzero) digits is 2400, while the sum is 24.

The square root of 221520345 is about 14883.5595540852. The cubic root of 221520345 is about 605.0684939414.

Adding to 221520345 its reverse (543025122), we get a palindrome (764545467).

The spelling of 221520345 in words is "two hundred twenty-one million, five hundred twenty thousand, three hundred forty-five".