261557550 has 36 divisors (see below), whose sum is σ = 702719160. Its totient is φ = 69748560.

The previous prime is 261557503. The next prime is 261557557. The reversal of 261557550 is 55755162.

It is a happy number.

261557550 is a `hidden beast` number, since 26 + 15 + 575 + 50 = 666.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261557557) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 290170 + ... + 291069.

Almost surely, 2^261557550 is an apocalyptic number.

261557550 is an abundant number, since it is smaller than the sum of its proper divisors (441161610).

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

261557550 is a wasteful number, since it uses less digits than its factorization.

261557550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 581257 (or 581249 counting only the distinct ones).

The product of its (nonzero) digits is 52500, while the sum is 36.

The square root of 261557550 is about 16172.7409550762. The cubic root of 261557550 is about 639.5223894321.

The spelling of 261557550 in words is "two hundred sixty-one million, five hundred fifty-seven thousand, five hundred fifty".