81539071 has 4 divisors (see below), whose sum is σ = 85084272. Its totient is φ = 77993872.

The previous prime is 81539063. The next prime is 81539099. The reversal of 81539071 is 17093518.

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 81539071 - 2³ = 81539063 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81599071) 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, 1772566 + ... + 1772611.

It is an arithmetic number, because the mean of its divisors is an integer number (21271068).

Almost surely, 2^81539071 is an apocalyptic number.

81539071 is a deficient number, since it is larger than the sum of its proper divisors (3545201).

81539071 is a wasteful number, since it uses less digits than its factorization.

81539071 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3545200.

The product of its (nonzero) digits is 7560, while the sum is 34.

The square root of 81539071 is about 9029.8987258994. The cubic root of 81539071 is about 433.6325951875.

The spelling of 81539071 in words is "eighty-one million, five hundred thirty-nine thousand, seventy-one".