261618066 has 64 divisors (see below), whose sum is σ = 617880960. Its totient is φ = 81768960.

The previous prime is 261618047. The next prime is 261618067. The reversal of 261618066 is 660816162.

It is a self number, because there is not a number n which added to its sum of digits gives 261618066.

It is not an unprimeable number, because it can be changed into a prime (261618067) 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, 478005 + ... + 478551.

It is an arithmetic number, because the mean of its divisors is an integer number (9654390).

Almost surely, 2^261618066 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261618066, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (308940480).

261618066 is an abundant number, since it is smaller than the sum of its proper divisors (356262894).

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

261618066 is a wasteful number, since it uses less digits than its factorization.

261618066 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1096 (or 1090 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 36.

The square root of 261618066 is about 16174.6117727753. The cubic root of 261618066 is about 639.5717072624.

The spelling of 261618066 in words is "two hundred sixty-one million, six hundred eighteen thousand, sixty-six".