81949729680 has 480 divisors, whose sum is σ = 339343280640. Its totient is φ = 17258987520.

The previous prime is 81949729649. The next prime is 81949729691. The reversal of 81949729680 is 8692794918.

81949729680 is a `hidden beast` number, since 81 + 9 + 497 + 2 + 9 + 68 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 60212200 + ... + 60213560.

It is an arithmetic number, because the mean of its divisors is an integer number (706965168).

Almost surely, 2^81949729680 is an apocalyptic number.

81949729680 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 81949729680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (169671640320).

81949729680 is an abundant number, since it is smaller than the sum of its proper divisors (257393550960).

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

81949729680 is a wasteful number, since it uses less digits than its factorization.

81949729680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2319 (or 2310 counting only the distinct ones).

The product of its (nonzero) digits is 15676416, while the sum is 63.

The spelling of 81949729680 in words is "eighty-one billion, nine hundred forty-nine million, seven hundred twenty-nine thousand, six hundred eighty".