81421775297856 has 2688 divisors, whose sum is σ = 313173894758400. Its totient is φ = 20239507169280.

The previous prime is 81421775297851. The next prime is 81421775297861. The reversal of 81421775297856 is 65879257712418.

81421775297856 is a `hidden beast` number, since 8 + 1 + 4 + 2 + 17 + 7 + 529 + 7 + 85 + 6 = 666.

It is an interprime number because it is at equal distance from previous prime (81421775297851) and next prime (81421775297861).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81421775297851) by changing a digit.

It is a polite number, since it can be written in 383 ways as a sum of consecutive naturals, for example, 641116340865 + ... + 641116340991.

Almost surely, 2^{81421775297856} is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81421775297856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (156586947379200).

81421775297856 is an abundant number, since it is smaller than the sum of its proper divisors (231752119460544).

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

81421775297856 is a wasteful number, since it uses less digits than its factorization.

81421775297856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 370 (or 325 counting only the distinct ones).

The product of its digits is 474163200, while the sum is 72.

The spelling of 81421775297856 in words is "eighty-one trillion, four hundred twenty-one billion, seven hundred seventy-five million, two hundred ninety-seven thousand, eight hundred fifty-six".