81979672320 has 720 divisors, whose sum is σ = 361073254080. Its totient is φ = 17294819328.

The previous prime is 81979672297. The next prime is 81979672331. The reversal of 81979672320 is 2327697918.

81979672320 is a `hidden beast` number, since 81 + 97 + 96 + 72 + 320 = 666.

It is a tau number, because it is divible by the number of its divisors (720).

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 79 ways as a sum of consecutive naturals, for example, 9430536 + ... + 9439224.

Almost surely, 2^81979672320 is an apocalyptic number.

81979672320 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 81979672320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (180536627040).

81979672320 is an abundant number, since it is smaller than the sum of its proper divisors (279093581760).

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

81979672320 is a wasteful number, since it uses less digits than its factorization.

81979672320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8742 (or 8719 counting only the distinct ones).

The product of its (nonzero) digits is 2286144, while the sum is 54.

The spelling of 81979672320 in words is "eighty-one billion, nine hundred seventy-nine million, six hundred seventy-two thousand, three hundred twenty".