81005571 has 12 divisors (see below), whose sum is σ = 119216448. Its totient is φ = 52984464.

The previous prime is 81005567. The next prime is 81005591. The reversal of 81005571 is 17550018.

81005571 is a `hidden beast` number, since 8 + 100 + 557 + 1 = 666.

It is not a de Polignac number, because 81005571 - 2² = 81005567 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81005501) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 84435 + ... + 85388.

It is an arithmetic number, because the mean of its divisors is an integer number (9934704).

Almost surely, 2^81005571 is an apocalyptic number.

81005571 is a deficient number, since it is larger than the sum of its proper divisors (38210877).

81005571 is a wasteful number, since it uses less digits than its factorization.

81005571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 169882 (or 169879 counting only the distinct ones).

The product of its (nonzero) digits is 1400, while the sum is 27.

The square root of 81005571 is about 9000.3094946785. The cubic root of 81005571 is about 432.6847903369.

Adding to 81005571 its reverse (17550018), we get a palindrome (98555589).

The spelling of 81005571 in words is "eighty-one million, five thousand, five hundred seventy-one".