261015840 has 144 divisors (see below), whose sum is σ = 912647736. Its totient is φ = 67891200.

The previous prime is 261015817. The next prime is 261015847. The reversal of 261015840 is 48510162.

261015840 is a `hidden beast` number, since 2 + 610 + 1 + 5 + 8 + 40 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 186158736 + 74857104 = 13644^2 + 8652^2 .

It is a tau number, because it is divible by the number of its divisors (144).

It is not an unprimeable number, because it can be changed into a prime (261015847) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 56830 + ... + 61250.

Almost surely, 2^261015840 is an apocalyptic number.

261015840 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 261015840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (456323868).

261015840 is an abundant number, since it is smaller than the sum of its proper divisors (651631896).

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

261015840 is a wasteful number, since it uses less digits than its factorization.

261015840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4483 (or 4472 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 261015840 is about 16155.9846496585. The cubic root of 261015840 is about 639.0805808436.

The spelling of 261015840 in words is "two hundred sixty-one million, fifteen thousand, eight hundred forty".