81866421161280 has 448 divisors, whose sum is σ = 331792752476160. Its totient is φ = 18614351923200.

The previous prime is 81866421161237. The next prime is 81866421161281. The reversal of 81866421161280 is 8216112466818.

81866421161280 is a `hidden beast` number, since 8 + 1 + 8 + 6 + 6 + 4 + 2 + 11 + 612 + 8 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (448).

It is a super-2 number, since 2×81866421161280² (a number of 29 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 not an unprimeable number, because it can be changed into a prime (81866421161281) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 8008195 + ... + 15095165.

Almost surely, 2^{81866421161280} is an apocalyptic number.

81866421161280 is a gapful number since it is divisible by the number (80) 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 81866421161280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (165896376238080).

81866421161280 is an abundant number, since it is smaller than the sum of its proper divisors (249926331314880).

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

81866421161280 is a wasteful number, since it uses less digits than its factorization.

81866421161280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7087195 (or 7087179 counting only the distinct ones).

The product of its (nonzero) digits is 1769472, while the sum is 54.

The spelling of 81866421161280 in words is "eighty-one trillion, eight hundred sixty-six billion, four hundred twenty-one million, one hundred sixty-one thousand, two hundred eighty".