81725639 has 4 divisors (see below), whose sum is σ = 81755400. Its totient is φ = 81695880.

The previous prime is 81725627. The next prime is 81725747. The reversal of 81725639 is 93652718.

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 81725639 - 2²⁴ = 64948423 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81725596 and 81725605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81722639) 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, 10289 + ... + 16410.

It is an arithmetic number, because the mean of its divisors is an integer number (20438850).

Almost surely, 2^81725639 is an apocalyptic number.

81725639 is a deficient number, since it is larger than the sum of its proper divisors (29761).

81725639 is a wasteful number, since it uses less digits than its factorization.

81725639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29760.

The product of its digits is 90720, while the sum is 41.

The square root of 81725639 is about 9040.2233932575. The cubic root of 81725639 is about 433.9630720985.

The spelling of 81725639 in words is "eighty-one million, seven hundred twenty-five thousand, six hundred thirty-nine".