261247211280 has 320 divisors, whose sum is σ = 1008190828800. Its totient is φ = 61620756480.

The previous prime is 261247211261. The next prime is 261247211339. The reversal of 261247211280 is 82112742162.

261247211280 is a `hidden beast` number, since 2 + 61 + 2 + 472 + 1 + 128 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

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 63 ways as a sum of consecutive naturals, for example, 730536 + ... + 1027704.

It is an arithmetic number, because the mean of its divisors is an integer number (3150596340).

Almost surely, 2^261247211280 is an apocalyptic number.

261247211280 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 261247211280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (504095414400).

261247211280 is an abundant number, since it is smaller than the sum of its proper divisors (746943617520).

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

261247211280 is a wasteful number, since it uses less digits than its factorization.

261247211280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 297239 (or 297227 counting only the distinct ones).

The product of its (nonzero) digits is 21504, while the sum is 36.

The spelling of 261247211280 in words is "two hundred sixty-one billion, two hundred forty-seven million, two hundred eleven thousand, two hundred eighty".