261650505666 has 128 divisors (see below), whose sum is σ = 603176232960. Its totient is φ = 74892224000.

The previous prime is 261650505659. The next prime is 261650505671. The reversal of 261650505666 is 666505056162.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 64238206 + ... + 64242278.

It is an arithmetic number, because the mean of its divisors is an integer number (4712314320).

Almost surely, 2^261650505666 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261650505666, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (301588116480).

261650505666 is an abundant number, since it is smaller than the sum of its proper divisors (341525727294).

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

261650505666 is a wasteful number, since it uses less digits than its factorization.

261650505666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4632.

The product of its (nonzero) digits is 1944000, while the sum is 48.

The spelling of 261650505666 in words is "two hundred sixty-one billion, six hundred fifty million, five hundred five thousand, six hundred sixty-six".