261660 has 72 divisors (see below), whose sum is σ = 861840. Its totient is φ = 59136.

The previous prime is 261643. The next prime is 261673. The reversal of 261660 is 66162.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a zygodrome in base 2.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2896 + ... + 2984.

It is an arithmetic number, because the mean of its divisors is an integer number (11970).

2²⁶¹⁶⁶⁰ is an apocalyptic number.

261660 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 261660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (430920).

261660 is an abundant number, since it is smaller than the sum of its proper divisors (600180).

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

261660 is a wasteful number, since it uses less digits than its factorization.

261660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115 (or 106 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 261660 is about 511.5271253805. The cubic root of 261660 is about 63.9605877134.

The spelling of 261660 in words is "two hundred sixty-one thousand, six hundred sixty".