81896209920 has 560 divisors, whose sum is σ = 336515113440. Its totient is φ = 18716147712.

The previous prime is 81896209891. The next prime is 81896209939. The reversal of 81896209920 is 2990269818.

81896209920 is a `hidden beast` number, since 8 + 1 + 8 + 9 + 620 + 9 + 9 + 2 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (560).

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 55 ways as a sum of consecutive naturals, for example, 13060546 + ... + 13066814.

Almost surely, 2^81896209920 is an apocalyptic number.

81896209920 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 81896209920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (168257556720).

81896209920 is an abundant number, since it is smaller than the sum of its proper divisors (254618903520).

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

81896209920 is an frugal number, since it uses more digits than its factorization.

81896209920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6317 (or 6286 counting only the distinct ones).

The product of its (nonzero) digits is 1119744, while the sum is 54.

The spelling of 81896209920 in words is "eighty-one billion, eight hundred ninety-six million, two hundred nine thousand, nine hundred twenty".