261557 has 2 divisors, whose sum is σ = 261558. Its totient is φ = 261556.

The previous prime is 261529. The next prime is 261563. The reversal of 261557 is 755162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 164836 + 96721 = 406^2 + 311^2 .

It is a cyclic number.

It is not a de Polignac number, because 261557 - 2⁸ = 261301 is a prime.

It is a Chen prime.

It is an Ulam number.

It is a nialpdrome in base 8.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261577) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130778 + 130779.

It is an arithmetic number, because the mean of its divisors is an integer number (130779).

2²⁶¹⁵⁵⁷ is an apocalyptic number.

It is an amenable number.

261557 is a deficient number, since it is larger than the sum of its proper divisors (1).

261557 is an equidigital number, since it uses as much as digits as its factorization.

261557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2100, while the sum is 26.

The square root of 261557 is about 511.4264365478. The cubic root of 261557 is about 63.9521941172.

It can be divided in two parts, 26155 and 7, that added together give a palindrome (26162).

The spelling of 261557 in words is "two hundred sixty-one thousand, five hundred fifty-seven".