261666618 has 64 divisors (see below), whose sum is σ = 571536000. Its totient is φ = 79552512.

The previous prime is 261666617. The next prime is 261666631. The reversal of 261666618 is 816666162.

It is a self number, because there is not a number n which added to its sum of digits gives 261666618.

It is not an unprimeable number, because it can be changed into a prime (261666617) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 524133 + ... + 524631.

It is an arithmetic number, because the mean of its divisors is an integer number (8930250).

Almost surely, 2^261666618 is an apocalyptic number.

261666618 is an abundant number, since it is smaller than the sum of its proper divisors (309869382).

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

261666618 is a wasteful number, since it uses less digits than its factorization.

261666618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 671.

The product of its digits is 124416, while the sum is 42.

The square root of 261666618 is about 16176.1125737923. The cubic root of 261666618 is about 639.6112694701.

The spelling of 261666618 in words is "two hundred sixty-one million, six hundred sixty-six thousand, six hundred eighteen".