81039989 has 4 divisors (see below), whose sum is σ = 81084780. Its totient is φ = 80995200.

The previous prime is 81039979. The next prime is 81040049. The reversal of 81039989 is 98993018.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 98993018 = 2 ⋅49496509.

It can be written as a sum of positive squares in 2 ways, for example, as 51696100 + 29343889 = 7190^2 + 5417^2 .

It is a cyclic number.

It is not a de Polignac number, because 81039989 - 2⁸ = 81039733 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81039979) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19562 + ... + 23339.

It is an arithmetic number, because the mean of its divisors is an integer number (20271195).

Almost surely, 2^81039989 is an apocalyptic number.

It is an amenable number.

81039989 is a deficient number, since it is larger than the sum of its proper divisors (44791).

81039989 is a wasteful number, since it uses less digits than its factorization.

81039989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44790.

The product of its (nonzero) digits is 139968, while the sum is 47.

The square root of 81039989 is about 9002.2213369812. The cubic root of 81039989 is about 432.7460619930.

It can be divided in two parts, 81039 and 989, that added together give a palindrome (82028).

The spelling of 81039989 in words is "eighty-one million, thirty-nine thousand, nine hundred eighty-nine".