81572705 has 4 divisors (see below), whose sum is σ = 97887252. Its totient is φ = 65258160.

The previous prime is 81572669. The next prime is 81572713. The reversal of 81572705 is 50727518.

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

It can be written as a sum of positive squares in 2 ways, for example, as 17380561 + 64192144 = 4169^2 + 8012^2 .

It is not a de Polignac number, because 81572705 - 2¹⁰ = 81571681 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8157266 + ... + 8157275.

It is an arithmetic number, because the mean of its divisors is an integer number (24471813).

Almost surely, 2^81572705 is an apocalyptic number.

It is an amenable number.

81572705 is a deficient number, since it is larger than the sum of its proper divisors (16314547).

81572705 is a wasteful number, since it uses less digits than its factorization.

81572705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16314546.

The product of its (nonzero) digits is 19600, while the sum is 35.

The square root of 81572705 is about 9031.7609025040. The cubic root of 81572705 is about 433.6922099368.

The spelling of 81572705 in words is "eighty-one million, five hundred seventy-two thousand, seven hundred five".