261581040 has 480 divisors, whose sum is σ = 1103072256. Its totient is φ = 54190080.

The previous prime is 261581029. The next prime is 261581041. The reversal of 261581040 is 40185162.

261581040 is a `hidden beast` number, since 2 + 615 + 8 + 1 + 0 + 40 = 666.

It is a junction number, because it is equal to n+sod(n) for n = 261580995 and 261581013.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261581041) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 3684205 + ... + 3684275.

Almost surely, 2^261581040 is an apocalyptic number.

261581040 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 261581040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (551536128).

261581040 is an abundant number, since it is smaller than the sum of its proper divisors (841491216).

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

261581040 is a wasteful number, since it uses less digits than its factorization.

261581040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 157 (or 148 counting only the distinct ones).

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

The square root of 261581040 is about 16173.4671607544. The cubic root of 261581040 is about 639.5415336335.

The spelling of 261581040 in words is "two hundred sixty-one million, five hundred eighty-one thousand, forty".