261191915520 has 768 divisors, whose sum is σ = 913522821120. Its totient is φ = 63531122688.

The previous prime is 261191915519. The next prime is 261191915587. The reversal of 261191915520 is 25519191162.

It is a tau number, because it is divible by the number of its divisors (768).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2535843789 + ... + 2535843891.

It is an arithmetic number, because the mean of its divisors is an integer number (1189482840).

Almost surely, 2^261191915520 is an apocalyptic number.

261191915520 is a gapful number since it is divisible by the number (20) 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 261191915520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (456761410560).

261191915520 is an abundant number, since it is smaller than the sum of its proper divisors (652330905600).

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

261191915520 is a wasteful number, since it uses less digits than its factorization.

261191915520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 290 (or 270 counting only the distinct ones).

The product of its (nonzero) digits is 48600, while the sum is 42.

It can be divided in two parts, 261191 and 915520, that added together give a palindrome (1176711).

The spelling of 261191915520 in words is "two hundred sixty-one billion, one hundred ninety-one million, nine hundred fifteen thousand, five hundred twenty".