261008640 has 216 divisors, whose sum is σ = 915139680. Its totient is φ = 68677632.

The previous prime is 261008621. The next prime is 261008647. The reversal of 261008640 is 46800162.

261008640 is a `hidden beast` number, since 2 + 6 + 10 + 0 + 8 + 640 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261008647) 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, 1601199 + ... + 1601361.

Almost surely, 2^261008640 is an apocalyptic number.

261008640 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 261008640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (457569840).

261008640 is an abundant number, since it is smaller than the sum of its proper divisors (654131040).

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

261008640 is a wasteful number, since it uses less digits than its factorization.

261008640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 329 (or 312 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 27.

The square root of 261008640 is about 16155.7618204775. The cubic root of 261008640 is about 639.0747045431.

The spelling of 261008640 in words is "two hundred sixty-one million, eight thousand, six hundred forty".