261281064960 has 432 divisors, whose sum is σ = 940576209300. Its totient is φ = 69657034752.

The previous prime is 261281064917. The next prime is 261281065009. The reversal of 261281064960 is 69460182162.

261281064960 is a `hidden beast` number, since 26 + 128 + 10 + 6 + 496 + 0 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 260736869376 + 544195584 = 510624^2 + 23328^2 .

It is a tau number, because it is divible by the number of its divisors (432).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 67182696 + ... + 67186584.

Almost surely, 2^261281064960 is an apocalyptic number.

261281064960 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 261281064960, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (470288104650).

261281064960 is an abundant number, since it is smaller than the sum of its proper divisors (679295144340).

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

261281064960 is an frugal number, since it uses more digits than its factorization.

261281064960 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3940 (or 3899 counting only the distinct ones).

The product of its (nonzero) digits is 248832, while the sum is 45.

The spelling of 261281064960 in words is "two hundred sixty-one billion, two hundred eighty-one million, sixty-four thousand, nine hundred sixty".