261840564 has 72 divisors (see below), whose sum is σ = 692775720. Its totient is φ = 83296512.

The previous prime is 261840559. The next prime is 261840571. The reversal of 261840564 is 465048162.

It can be written as a sum of positive squares in 4 ways, for example, as 86490000 + 175350564 = 9300^2 + 13242^2 .

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

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, 68742 + ... + 72450.

It is an arithmetic number, because the mean of its divisors is an integer number (9621885).

Almost surely, 2^261840564 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261840564, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (346387860).

261840564 is an abundant number, since it is smaller than the sum of its proper divisors (430935156).

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

261840564 is a wasteful number, since it uses less digits than its factorization.

261840564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3809 (or 3804 counting only the distinct ones).

The product of its (nonzero) digits is 46080, while the sum is 36.

The square root of 261840564 is about 16181.4883122660. The cubic root of 261840564 is about 639.7529678119.

The spelling of 261840564 in words is "two hundred sixty-one million, eight hundred forty thousand, five hundred sixty-four".