261378539815680 has 1440 divisors, whose sum is σ = 1090207856352384. Its totient is φ = 58553378537472.

The previous prime is 261378539815643. The next prime is 261378539815681. The reversal of 261378539815680 is 86518935873162.

261378539815680 is a `hidden beast` number, since 2 + 6 + 1 + 3 + 7 + 8 + 5 + 398 + 156 + 80 = 666.

It is a tau number, because it is divible by the number of its divisors (1440).

It is a Harshad number since it is a multiple of its sum of digits (72).

It is a junction number, because it is equal to n+sod(n) for n = 261378539815599 and 261378539815608.

It is not an unprimeable number, because it can be changed into a prime (261378539815681) by changing a digit.

It is a polite number, since it can be written in 159 ways as a sum of consecutive naturals, for example, 42042547932 + ... + 42042554148.

Almost surely, 2^{261378539815680} is an apocalyptic number.

261378539815680 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 261378539815680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (545103928176192).

261378539815680 is an abundant number, since it is smaller than the sum of its proper divisors (828829316536704).

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

261378539815680 is a wasteful number, since it uses less digits than its factorization.

261378539815680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7403 (or 7380 counting only the distinct ones).

The product of its (nonzero) digits is 522547200, while the sum is 72.

The spelling of 261378539815680 in words is "two hundred sixty-one trillion, three hundred seventy-eight billion, five hundred thirty-nine million, eight hundred fifteen thousand, six hundred eighty".