81789708121 has 9 divisors (see below), whose sum is σ = 89904542133. Its totient is φ = 74351420220.

The previous prime is 81789708113. The next prime is 81789708157. The reversal of 81789708121 is 12180798718.

The square root of 81789708121 is 285989.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 81789708121 - 2³ = 81789708113 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81789709121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 3132880 + ... + 3158878.

Almost surely, 2^81789708121 is an apocalyptic number.

81789708121 is the 285989-th square number.

81789708121 is the 142995-th centered octagonal number.

It is an amenable number.

81789708121 is a deficient number, since it is larger than the sum of its proper divisors (8114834012).

81789708121 is an frugal number, since it uses more digits than its factorization.

81789708121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52020 (or 26010 counting only the distinct ones).

The product of its (nonzero) digits is 451584, while the sum is 52.

The spelling of 81789708121 in words is "eighty-one billion, seven hundred eighty-nine million, seven hundred eight thousand, one hundred twenty-one".