261664242858 has 128 divisors (see below), whose sum is σ = 600341414400. Its totient is φ = 84440918016.

The previous prime is 261664242857. The next prime is 261664242901. The reversal of 261664242858 is 858242466162.

261664242858 is a `hidden beast` number, since 2 + 6 + 166 + 4 + 2 + 428 + 58 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is not an unprimeable number, because it can be changed into a prime (261664242857) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 107990635 + ... + 107993057.

It is an arithmetic number, because the mean of its divisors is an integer number (4690167300).

Almost surely, 2^261664242858 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261664242858, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (300170707200).

261664242858 is an abundant number, since it is smaller than the sum of its proper divisors (338677171542).

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

261664242858 is a wasteful number, since it uses less digits than its factorization.

261664242858 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2973 (or 2967 counting only the distinct ones).

The product of its digits is 8847360, while the sum is 54.

The spelling of 261664242858 in words is "two hundred sixty-one billion, six hundred sixty-four million, two hundred forty-two thousand, eight hundred fifty-eight".