261641556 has 96 divisors (see below), whose sum is σ = 746928000. Its totient is φ = 78543360.

The previous prime is 261641521. The next prime is 261641593. The reversal of 261641556 is 655146162.

261641556 is a `hidden beast` number, since 2 + 6 + 1 + 641 + 5 + 5 + 6 = 666.

261641556 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×261641556² = 136912607652202272, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nialpdrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 261641556.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 133270 + ... + 135218.

It is an arithmetic number, because the mean of its divisors is an integer number (7780500).

Almost surely, 2^261641556 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 261641556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (373464000).

261641556 is an abundant number, since it is smaller than the sum of its proper divisors (485286444).

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

261641556 is a wasteful number, since it uses less digits than its factorization.

261641556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2086 (or 2078 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

The square root of 261641556 is about 16175.3378944614. The cubic root of 261641556 is about 639.5908485116.

The spelling of 261641556 in words is "two hundred sixty-one million, six hundred forty-one thousand, five hundred fifty-six".