261601 has 2 divisors, whose sum is σ = 261602. Its totient is φ = 261600.

The previous prime is 261593. The next prime is 261619. The reversal of 261601 is 106162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 159201 + 102400 = 399^2 + 320^2 .

It is a cyclic number.

It is not a de Polignac number, because 261601 - 2³ = 261593 is a prime.

It is an Ulam number.

261601 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (261631) 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, 130800 + 130801.

It is an arithmetic number, because the mean of its divisors is an integer number (130801).

2²⁶¹⁶⁰¹ is an apocalyptic number.

It is an amenable number.

261601 is a deficient number, since it is larger than the sum of its proper divisors (1).

261601 is an equidigital number, since it uses as much as digits as its factorization.

261601 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 261601 is about 511.4694516782. The cubic root of 261601 is about 63.9557800007.

Adding to 261601 its reverse (106162), we get a palindrome (367763).

The spelling of 261601 in words is "two hundred sixty-one thousand, six hundred one".