261116521 has 2 divisors, whose sum is σ = 261116522. Its totient is φ = 261116520.

The previous prime is 261116519. The next prime is 261116579. The reversal of 261116521 is 125611162.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 260984025 + 132496 = 16155^2 + 364^2 .

It is a cyclic number.

It is not a de Polignac number, because 261116521 - 2¹ = 261116519 is a prime.

Together with 261116519, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (261116321) 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 as a sum of consecutive naturals, namely, 130558260 + 130558261.

It is an arithmetic number, because the mean of its divisors is an integer number (130558261).

Almost surely, 2^261116521 is an apocalyptic number.

It is an amenable number.

261116521 is a deficient number, since it is larger than the sum of its proper divisors (1).

261116521 is an equidigital number, since it uses as much as digits as its factorization.

261116521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 720, while the sum is 25.

The square root of 261116521 is about 16159.1002534176. The cubic root of 261116521 is about 639.1627406092.

Adding to 261116521 its reverse (125611162), we get a palindrome (386727683).

The spelling of 261116521 in words is "two hundred sixty-one million, one hundred sixteen thousand, five hundred twenty-one".