261520740 has 108 divisors (see below), whose sum is σ = 859094964. Its totient is φ = 64366848.

The previous prime is 261520729. The next prime is 261520771. The reversal of 261520740 is 47025162.

261520740 is a `hidden beast` number, since 2 + 615 + 2 + 0 + 7 + 40 = 666.

It can be written as a sum of positive squares in 6 ways, for example, as 31270464 + 230250276 = 5592^2 + 15174^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 26122 + ... + 34718.

It is an arithmetic number, because the mean of its divisors is an integer number (7954583).

Almost surely, 2^261520740 is an apocalyptic number.

261520740 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 261520740, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (429547482).

261520740 is an abundant number, since it is smaller than the sum of its proper divisors (597574224).

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

261520740 is a wasteful number, since it uses less digits than its factorization.

261520740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8638 (or 8620 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 27.

The square root of 261520740 is about 16171.6028890151. The cubic root of 261520740 is about 639.4923872094.

The spelling of 261520740 in words is "two hundred sixty-one million, five hundred twenty thousand, seven hundred forty".