81996963840 has 672 divisors, whose sum is σ = 315461087136. Its totient is φ = 19534970880.

The previous prime is 81996963793. The next prime is 81996963859. The reversal of 81996963840 is 4836969918.

It is a happy number.

81996963840 is a `hidden beast` number, since 8 + 199 + 69 + 6 + 384 + 0 = 666.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 296017782 + ... + 296018058.

Almost surely, 2^81996963840 is an apocalyptic number.

81996963840 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 81996963840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (157730543568).

81996963840 is an abundant number, since it is smaller than the sum of its proper divisors (233464123296).

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

81996963840 is a wasteful number, since it uses less digits than its factorization.

81996963840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 398 (or 371 counting only the distinct ones).

The product of its (nonzero) digits is 20155392, while the sum is 63.

The spelling of 81996963840 in words is "eighty-one billion, nine hundred ninety-six million, nine hundred sixty-three thousand, eight hundred forty".