81489375581 has 4 divisors (see below), whose sum is σ = 81490078752. Its totient is φ = 81488672412.

The previous prime is 81489375533. The next prime is 81489375593. The reversal of 81489375581 is 18557398418.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 81489375581 - 2²² = 81485181277 is a prime.

It is a super-2 number, since 2×81489375581² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81489375581.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81489375181) 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 3 ways as a sum of consecutive naturals, for example, 132065 + ... + 424758.

It is an arithmetic number, because the mean of its divisors is an integer number (20372519688).

Almost surely, 2^81489375581 is an apocalyptic number.

It is an amenable number.

81489375581 is a deficient number, since it is larger than the sum of its proper divisors (703171).

81489375581 is a wasteful number, since it uses less digits than its factorization.

81489375581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 703170.

The product of its digits is 9676800, while the sum is 59.

It can be divided in two parts, 8148937 and 5581, that added together give a palindrome (8154518).

The spelling of 81489375581 in words is "eighty-one billion, four hundred eighty-nine million, three hundred seventy-five thousand, five hundred eighty-one".