81221757345144 has 48 divisors (see below), whose sum is σ = 236896792259400. Its totient is φ = 24991309952064.

The previous prime is 81221757345137. The next prime is 81221757345167. The reversal of 81221757345144 is 44154375712218.

It is a happy number.

81221757345144 is a `hidden beast` number, since 8 + 1 + 2 + 2 + 17 + 573 + 4 + 51 + 4 + 4 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 43387689954 + ... + 43387691825.

Almost surely, 2^{81221757345144} is an apocalyptic number.

It is an amenable number.

81221757345144 is an abundant number, since it is smaller than the sum of its proper divisors (155675034914256).

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

81221757345144 is a wasteful number, since it uses less digits than its factorization.

81221757345144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 86775381804 (or 86775381797 counting only the distinct ones).

The product of its digits is 7526400, while the sum is 54.

The spelling of 81221757345144 in words is "eighty-one trillion, two hundred twenty-one billion, seven hundred fifty-seven million, three hundred forty-five thousand, one hundred forty-four".