261609216 has 144 divisors (see below), whose sum is σ = 768216960. Its totient is φ = 78376960.

The previous prime is 261609167. The next prime is 261609221. The reversal of 261609216 is 612906162.

It is a super-2 number, since 2×261609216² = 136878763792269312, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1461415 + ... + 1461593.

It is an arithmetic number, because the mean of its divisors is an integer number (5334840).

Almost surely, 2^261609216 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 261609216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (384108480).

261609216 is an abundant number, since it is smaller than the sum of its proper divisors (506607744).

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

261609216 is a wasteful number, since it uses less digits than its factorization.

261609216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 382 (or 368 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 33.

The square root of 261609216 is about 16174.3381935707. The cubic root of 261609216 is about 639.5644953835.

The spelling of 261609216 in words is "two hundred sixty-one million, six hundred nine thousand, two hundred sixteen".