81939489 has 8 divisors (see below), whose sum is σ = 110379360. Its totient is φ = 54062976.

The previous prime is 81939463. The next prime is 81939503. The reversal of 81939489 is 98493918.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-81939489 is a prime.

It is a super-2 number, since 2×81939489² = 13428159715162242, which contains 22 as substring.

It is a Smith number, since the sum of its digits (51) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (81939449) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 140499 + ... + 141080.

It is an arithmetic number, because the mean of its divisors is an integer number (13797420).

Almost surely, 2^81939489 is an apocalyptic number.

It is an amenable number.

81939489 is a deficient number, since it is larger than the sum of its proper divisors (28439871).

81939489 is a wasteful number, since it uses less digits than its factorization.

81939489 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 281679.

The product of its digits is 559872, while the sum is 51.

The square root of 81939489 is about 9052.0433604794. The cubic root of 81939489 is about 434.3412568651.

It can be divided in two parts, 81939 and 489, that added together give a palindrome (82428).

The spelling of 81939489 in words is "eighty-one million, nine hundred thirty-nine thousand, four hundred eighty-nine".