261505517280 has 384 divisors, whose sum is σ = 957496329216. Its totient is φ = 58757529600.

The previous prime is 261505517269. The next prime is 261505517293. The reversal of 261505517280 is 82715505162.

261505517280 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a hoax number, since the sum of its digits (42) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 81186070 + ... + 81189290.

It is an arithmetic number, because the mean of its divisors is an integer number (2493480024).

Almost surely, 2^261505517280 is an apocalyptic number.

261505517280 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 261505517280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (478748164608).

261505517280 is an abundant number, since it is smaller than the sum of its proper divisors (695990811936).

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

261505517280 is a wasteful number, since it uses less digits than its factorization.

261505517280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3650 (or 3642 counting only the distinct ones).

The product of its (nonzero) digits is 168000, while the sum is 42.

The spelling of 261505517280 in words is "two hundred sixty-one billion, five hundred five million, five hundred seventeen thousand, two hundred eighty".