261561216 has 96 divisors (see below), whose sum is σ = 808262280. Its totient is φ = 74726400.

The previous prime is 261561197. The next prime is 261561227. The reversal of 261561216 is 612165162.

261561216 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (96).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 11866 + ... + 25766.

Almost surely, 2^261561216 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 261561216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (404131140).

261561216 is an abundant number, since it is smaller than the sum of its proper divisors (546701064).

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

261561216 is a wasteful number, since it uses less digits than its factorization.

261561216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13932 (or 13913 counting only the distinct ones).

The product of its digits is 4320, while the sum is 30.

The square root of 261561216 is about 16172.8542935377. The cubic root of 261561216 is about 639.5253772744.

It can be divided in two parts, 26156 and 1216, that added together give a palindrome (27372).

The spelling of 261561216 in words is "two hundred sixty-one million, five hundred sixty-one thousand, two hundred sixteen".