81539723 has 4 divisors (see below), whose sum is σ = 81558360. Its totient is φ = 81521088.

The previous prime is 81539707. The next prime is 81539729. The reversal of 81539723 is 32793518.

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 81539723 - 2⁴ = 81539707 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81539729) 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, 1211 + ... + 12827.

It is an arithmetic number, because the mean of its divisors is an integer number (20389590).

Almost surely, 2^81539723 is an apocalyptic number.

81539723 is a deficient number, since it is larger than the sum of its proper divisors (18637).

81539723 is a wasteful number, since it uses less digits than its factorization.

81539723 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18636.

The product of its digits is 45360, while the sum is 38.

The square root of 81539723 is about 9029.9348281148. The cubic root of 81539723 is about 433.6337509840.

The spelling of 81539723 in words is "eighty-one million, five hundred thirty-nine thousand, seven hundred twenty-three".