261406505065680 has 800 divisors, whose sum is σ = 1029696578951040. Its totient is φ = 60930302423040.

The previous prime is 261406505065649. The next prime is 261406505065709. The reversal of 261406505065680 is 86560505604162.

261406505065680 is a `hidden beast` number, since 2 + 6 + 1 + 4 + 0 + 6 + 5 + 0 + 506 + 56 + 80 = 666.

It is a super-2 number, since 2×261406505065680² (a number of 30 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 159 ways as a sum of consecutive naturals, for example, 3426760819 + ... + 3426837101.

Almost surely, 2^{261406505065680} is an apocalyptic number.

261406505065680 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 261406505065680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (514848289475520).

261406505065680 is an abundant number, since it is smaller than the sum of its proper divisors (768290073885360).

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

261406505065680 is a wasteful number, since it uses less digits than its factorization.

261406505065680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78481 (or 78466 counting only the distinct ones).

The product of its (nonzero) digits is 10368000, while the sum is 54.

The spelling of 261406505065680 in words is "two hundred sixty-one trillion, four hundred six billion, five hundred five million, sixty-five thousand, six hundred eighty".