81320217889 has 9 divisors (see below), whose sum is σ = 81787990323. Its totient is φ = 80855110512.

The previous prime is 81320217883. The next prime is 81320217907. The reversal of 81320217889 is 98871202318.

The square root of 81320217889 is 285167.

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

It can be written as a sum of positive squares in only one way, i.e., 67441493025 + 13878724864 = 259695^2 + 117808^2 .

It is not a de Polignac number, because 81320217889 - 2²⁹ = 80783346977 is a prime.

It is a super-2 number, since 2×81320217889² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81320217883) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 56747517 + ... + 56748949.

Almost surely, 2^81320217889 is an apocalyptic number.

81320217889 is the 285167-th square number.

81320217889 is the 142584-th centered octagonal number.

It is an amenable number.

81320217889 is a deficient number, since it is larger than the sum of its proper divisors (467772434).

81320217889 is an frugal number, since it uses more digits than its factorization.

81320217889 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3264 (or 1632 counting only the distinct ones).

The product of its (nonzero) digits is 387072, while the sum is 49.

Multiplying 81320217889 by its sum of digits (49), we get a square (3984690676561 = 1996169²).

It can be divided in two parts, 81320 and 217889, that added together give a square (299209 = 547²).

The spelling of 81320217889 in words is "eighty-one billion, three hundred twenty million, two hundred seventeen thousand, eight hundred eighty-nine".