261656581912 has 128 divisors (see below), whose sum is σ = 570859488000. Its totient is φ = 111186639360.

The previous prime is 261656581861. The next prime is 261656581913. The reversal of 261656581912 is 219185656162.

It is a self number, because there is not a number n which added to its sum of digits gives 261656581912.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261656581913) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 48122458 + ... + 48127894.

It is an arithmetic number, because the mean of its divisors is an integer number (4459839750).

Almost surely, 2^261656581912 is an apocalyptic number.

261656581912 is a gapful number since it is divisible by the number (22) 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 261656581912, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (285429744000).

261656581912 is an abundant number, since it is smaller than the sum of its proper divisors (309202906088).

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

261656581912 is a wasteful number, since it uses less digits than its factorization.

261656581912 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5849 (or 5845 counting only the distinct ones).

The product of its digits is 1555200, while the sum is 52.

The spelling of 261656581912 in words is "two hundred sixty-one billion, six hundred fifty-six million, five hundred eighty-one thousand, nine hundred twelve".