261985556 has 36 divisors (see below), whose sum is σ = 535418100. Its totient is φ = 111839616.

The previous prime is 261985513. The next prime is 261985561. The reversal of 261985556 is 655589162.

It can be written as a sum of positive squares in 2 ways, for example, as 32947600 + 229037956 = 5740^2 + 15134^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 261985556.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 50240 + ... + 55208.

It is an arithmetic number, because the mean of its divisors is an integer number (14872725).

Almost surely, 2^261985556 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261985556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (267709050).

261985556 is an abundant number, since it is smaller than the sum of its proper divisors (273432544).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

261985556 is a wasteful number, since it uses less digits than its factorization.

261985556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5256 (or 5247 counting only the distinct ones).

The product of its digits is 648000, while the sum is 47.

The square root of 261985556 is about 16185.9678734390. The cubic root of 261985556 is about 639.8710319558.

The spelling of 261985556 in words is "two hundred sixty-one million, nine hundred eighty-five thousand, five hundred fifty-six".