81680539 has 4 divisors (see below), whose sum is σ = 81927640. Its totient is φ = 81433440.

The previous prime is 81680531. The next prime is 81680593. The reversal of 81680539 is 93508618.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81680539 - 2³ = 81680531 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81680531) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 123054 + ... + 123715.

It is an arithmetic number, because the mean of its divisors is an integer number (20481910).

Almost surely, 2^81680539 is an apocalyptic number.

81680539 is a deficient number, since it is larger than the sum of its proper divisors (247101).

81680539 is a wasteful number, since it uses less digits than its factorization.

81680539 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 247100.

The product of its (nonzero) digits is 51840, while the sum is 40.

The square root of 81680539 is about 9037.7286416444. The cubic root of 81680539 is about 433.8832304230.

The spelling of 81680539 in words is "eighty-one million, six hundred eighty thousand, five hundred thirty-nine".