261866340 has 72 divisors (see below), whose sum is σ = 796493880. Its totient is φ = 69640704.

The previous prime is 261866333. The next prime is 261866357. The reversal of 261866340 is 43668162.

261866340 is a `hidden beast` number, since 2 + 6 + 18 + 6 + 634 + 0 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 31069476 + 230796864 = 5574^2 + 15192^2 .

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

It is a junction number, because it is equal to n+sod(n) for n = 261866295 and 261866304.

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, 71842 + ... + 75398.

It is an arithmetic number, because the mean of its divisors is an integer number (11062415).

Almost surely, 2^261866340 is an apocalyptic number.

261866340 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 261866340, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (398246940).

261866340 is an abundant number, since it is smaller than the sum of its proper divisors (534627540).

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

261866340 is a wasteful number, since it uses less digits than its factorization.

261866340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3981 (or 3976 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 36.

The square root of 261866340 is about 16182.2847583399. The cubic root of 261866340 is about 639.7739598884.

The spelling of 261866340 in words is "two hundred sixty-one million, eight hundred sixty-six thousand, three hundred forty".