81720545742758 has 64 divisors (see below), whose sum is σ = 142530069528000. Its totient is φ = 34822581281280.

The previous prime is 81720545742733. The next prime is 81720545742863. The reversal of 81720545742758 is 85724754502718.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 81720545742694 and 81720545742703.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 6572873 + ... + 14375108.

It is an arithmetic number, because the mean of its divisors is an integer number (2227032336375).

Almost surely, 2^{81720545742758} is an apocalyptic number.

81720545742758 is a deficient number, since it is larger than the sum of its proper divisors (60809523785242).

81720545742758 is a wasteful number, since it uses less digits than its factorization.

81720545742758 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20948217.

The product of its (nonzero) digits is 175616000, while the sum is 65.

The spelling of 81720545742758 in words is "eighty-one trillion, seven hundred twenty billion, five hundred forty-five million, seven hundred forty-two thousand, seven hundred fifty-eight".