81378842163840 has 384 divisors, whose sum is σ = 320429196032400. Its totient is φ = 18853378523136.

The previous prime is 81378842163691. The next prime is 81378842163907. The reversal of 81378842163840 is 4836124887318.

It is a happy number.

81378842163840 is a `hidden beast` number, since 8 + 1 + 3 + 78 + 8 + 421 + 63 + 84 + 0 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 6334322508864 + 75044519654976 = 2516808^2 + 8662824^2 .

It is a tau number, because it is divible by the number of its divisors (384).

It is a super-3 number, since 3×81378842163840³ (a number of 43 digits) contains 333 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 30691455 + ... + 33237374.

Almost surely, 2^{81378842163840} is an apocalyptic number.

81378842163840 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81378842163840 is an abundant number, since it is smaller than the sum of its proper divisors (239050353868560).

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

81378842163840 is a wasteful number, since it uses less digits than its factorization.

81378842163840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63928884 (or 63928869 counting only the distinct ones).

The product of its (nonzero) digits is 49545216, while the sum is 63.

The spelling of 81378842163840 in words is "eighty-one trillion, three hundred seventy-eight billion, eight hundred forty-two million, one hundred sixty-three thousand, eight hundred forty".