261566660 has 96 divisors (see below), whose sum is σ = 592220160. Its totient is φ = 96864768.

The previous prime is 261566659. The next prime is 261566671. The reversal of 261566660 is 66665162.

261566660 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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, 2059517 + ... + 2059643.

It is an arithmetic number, because the mean of its divisors is an integer number (6168960).

Almost surely, 2^261566660 is an apocalyptic number.

261566660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261566660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (296110080).

261566660 is an abundant number, since it is smaller than the sum of its proper divisors (330653500).

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

261566660 is a wasteful number, since it uses less digits than its factorization.

261566660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 285 (or 283 counting only the distinct ones).

The product of its (nonzero) digits is 77760, while the sum is 38.

The square root of 261566660 is about 16173.0225993783. The cubic root of 261566660 is about 639.5298141605.

The spelling of 261566660 in words is "two hundred sixty-one million, five hundred sixty-six thousand, six hundred sixty".