81099721056 has 48 divisors (see below), whose sum is σ = 212932320048. Its totient is φ = 27027456000.

The previous prime is 81099721051. The next prime is 81099721177. The reversal of 81099721056 is 65012799018.

It is a tau number, because it is divible by the number of its divisors (48).

It is a super-2 number, since 2×81099721056² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a junction number, because it is equal to n+sod(n) for n = 81099720996 and 81099721014.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81099721051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 372916 + ... + 548876.

It is an arithmetic number, because the mean of its divisors is an integer number (4436090001).

Almost surely, 2^81099721056 is an apocalyptic number.

It is an amenable number.

81099721056 is an abundant number, since it is smaller than the sum of its proper divisors (131832598992).

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

81099721056 is a wasteful number, since it uses less digits than its factorization.

81099721056 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 180775 (or 180767 counting only the distinct ones).

The product of its (nonzero) digits is 272160, while the sum is 48.

The spelling of 81099721056 in words is "eighty-one billion, ninety-nine million, seven hundred twenty-one thousand, fifty-six".