261739505664 has 1152 divisors, whose sum is σ = 1007393587200. Its totient is φ = 63541739520.

The previous prime is 261739505663. The next prime is 261739505669. The reversal of 261739505664 is 466505937162.

261739505664 is a `hidden beast` number, since 2 + 6 + 1 + 73 + 9 + 5 + 0 + 566 + 4 = 666.

It is a tau number, because it is divible by the number of its divisors (1152).

It is a self number, because there is not a number n which added to its sum of digits gives 261739505664.

It is not an unprimeable number, because it can be changed into a prime (261739505663) 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 95 ways as a sum of consecutive naturals, for example, 1370363809 + ... + 1370363999.

It is an arithmetic number, because the mean of its divisors is an integer number (874473600).

Almost surely, 2^261739505664 is an apocalyptic number.

261739505664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261739505664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (503696793600).

261739505664 is an abundant number, since it is smaller than the sum of its proper divisors (745654081536).

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

261739505664 is a wasteful number, since it uses less digits than its factorization.

261739505664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 301 (or 278 counting only the distinct ones).

The product of its (nonzero) digits is 8164800, while the sum is 54.

The spelling of 261739505664 in words is "two hundred sixty-one billion, seven hundred thirty-nine million, five hundred five thousand, six hundred sixty-four".