81221764120 has 64 divisors (see below), whose sum is σ = 209327742720. Its totient is φ = 27784558464.

The previous prime is 81221764097. The next prime is 81221764121. The reversal of 81221764120 is 2146712218.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81221764121) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 203362 + ... + 451441.

It is an arithmetic number, because the mean of its divisors is an integer number (3270745980).

Almost surely, 2^81221764120 is an apocalyptic number.

It is an amenable number.

81221764120 is an abundant number, since it is smaller than the sum of its proper divisors (128105978600).

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

81221764120 is a wasteful number, since it uses less digits than its factorization.

81221764120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 655264 (or 655260 counting only the distinct ones).

The product of its (nonzero) digits is 10752, while the sum is 34.

The spelling of 81221764120 in words is "eighty-one billion, two hundred twenty-one million, seven hundred sixty-four thousand, one hundred twenty".