261320221 has 2 divisors, whose sum is σ = 261320222. Its totient is φ = 261320220.

The previous prime is 261320207. The next prime is 261320237. The reversal of 261320221 is 122023162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 261307225 + 12996 = 16165^2 + 114^2 .

It is a cyclic number.

It is not a de Polignac number, because 261320221 - 2⁷ = 261320093 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261320201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130660110 + 130660111.

It is an arithmetic number, because the mean of its divisors is an integer number (130660111).

Almost surely, 2^261320221 is an apocalyptic number.

It is an amenable number.

261320221 is a deficient number, since it is larger than the sum of its proper divisors (1).

261320221 is an equidigital number, since it uses as much as digits as its factorization.

261320221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 261320221 is about 16165.4019745876. The cubic root of 261320221 is about 639.3289034756.

Adding to 261320221 its reverse (122023162), we get a palindrome (383343383).

The spelling of 261320221 in words is "two hundred sixty-one million, three hundred twenty thousand, two hundred twenty-one".