261585720 has 256 divisors, whose sum is σ = 965260800. Its totient is φ = 62484480.

The previous prime is 261585697. The next prime is 261585743. The reversal of 261585720 is 27585162.

It is a happy number.

261585720 is a `hidden beast` number, since 2 + 6 + 1 + 585 + 72 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (261585697) and next prime (261585743).

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 63 ways as a sum of consecutive naturals, for example, 1152247 + ... + 1152473.

It is an arithmetic number, because the mean of its divisors is an integer number (3770550).

Almost surely, 2^261585720 is an apocalyptic number.

261585720 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 261585720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (482630400).

261585720 is an abundant number, since it is smaller than the sum of its proper divisors (703675080).

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

261585720 is a wasteful number, since it uses less digits than its factorization.

261585720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 355 (or 345 counting only the distinct ones).

The product of its (nonzero) digits is 33600, while the sum is 36.

The square root of 261585720 is about 16173.6118415152. The cubic root of 261585720 is about 639.5453476670.

It can be divided in two parts, 26158 and 5720, that added together give a triangular number (31878 = T₂₅₂).

The spelling of 261585720 in words is "two hundred sixty-one million, five hundred eighty-five thousand, seven hundred twenty".