81709445 has 8 divisors (see below), whose sum is σ = 98560536. Its totient is φ = 65028096.

The previous prime is 81709423. The next prime is 81709471. The reversal of 81709445 is 54490718.

It can be written as a sum of positive squares in 4 ways, for example, as 13184161 + 68525284 = 3631^2 + 8278^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 81709445 - 2⁸ = 81709189 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 81709399 and 81709408.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 41372 + ... + 43301.

It is an arithmetic number, because the mean of its divisors is an integer number (12320067).

Almost surely, 2^81709445 is an apocalyptic number.

It is an amenable number.

81709445 is a deficient number, since it is larger than the sum of its proper divisors (16851091).

81709445 is a wasteful number, since it uses less digits than its factorization.

81709445 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84871.

The product of its (nonzero) digits is 40320, while the sum is 38.

The square root of 81709445 is about 9039.3276851766. The cubic root of 81709445 is about 433.9344068298.

The spelling of 81709445 in words is "eighty-one million, seven hundred nine thousand, four hundred forty-five".