261991536576 has 224 divisors, whose sum is σ = 884332382208. Its totient is φ = 66467036160.

The previous prime is 261991536563. The next prime is 261991536613. The reversal of 261991536576 is 675635199162.

It is a tau number, because it is divible by the number of its divisors (224).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 429651 + ... + 841773.

Almost surely, 2^261991536576 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 261991536576, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (442166191104).

261991536576 is an abundant number, since it is smaller than the sum of its proper divisors (622340845632).

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

261991536576 is a wasteful number, since it uses less digits than its factorization.

261991536576 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 412199 (or 412189 counting only the distinct ones).

The product of its digits is 18370800, while the sum is 60.

The spelling of 261991536576 in words is "two hundred sixty-one billion, nine hundred ninety-one million, five hundred thirty-six thousand, five hundred seventy-six".