221520317 has 2 divisors, whose sum is σ = 221520318. Its totient is φ = 221520316.

The previous prime is 221520307. The next prime is 221520347. The reversal of 221520317 is 713025122.

It is a happy number.

221520317 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 124970041 + 96550276 = 11179^2 + 9826^2 .

It is a cyclic number.

It is not a de Polignac number, because 221520317 - 2²² = 217326013 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 221520292 and 221520301.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221520307) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110760158 + 110760159.

It is an arithmetic number, because the mean of its divisors is an integer number (110760159).

Almost surely, 2^221520317 is an apocalyptic number.

It is an amenable number.

221520317 is a deficient number, since it is larger than the sum of its proper divisors (1).

221520317 is an equidigital number, since it uses as much as digits as its factorization.

221520317 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 840, while the sum is 23.

The square root of 221520317 is about 14883.5586134499. The cubic root of 221520317 is about 605.0684684480.

Adding to 221520317 its reverse (713025122), we get a palindrome (934545439).

The spelling of 221520317 in words is "two hundred twenty-one million, five hundred twenty thousand, three hundred seventeen".