261857125 has 16 divisors (see below), whose sum is σ = 328713840. Its totient is φ = 208257600.

The previous prime is 261857111. The next prime is 261857147. The reversal of 261857125 is 521758162.

It is a Cunningham number, because it is equal to 16182²+1.

It can be written as a sum of positive squares in 8 ways, for example, as 1 + 261857124 = 1^2 + 16182^2 .

It is not a de Polignac number, because 261857125 - 2⁷ = 261856997 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15571 + ... + 27679.

It is an arithmetic number, because the mean of its divisors is an integer number (20544615).

Almost surely, 2^261857125 is an apocalyptic number.

261857125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

261857125 is the 8650-th nonagonal number.

It is an amenable number.

261857125 is a deficient number, since it is larger than the sum of its proper divisors (66856715).

261857125 is a wasteful number, since it uses less digits than its factorization.

261857125 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12297 (or 12287 counting only the distinct ones).

The product of its digits is 33600, while the sum is 37.

The square root of 261857125 is about 16182.0000308985. Note that the first 4 decimals coincide. The cubic root of 261857125 is about 639.7664553141.

The spelling of 261857125 in words is "two hundred sixty-one million, eight hundred fifty-seven thousand, one hundred twenty-five".