81611571 has 4 divisors (see below), whose sum is σ = 108815432. Its totient is φ = 54407712.

The previous prime is 81611531. The next prime is 81611639. The reversal of 81611571 is 17511618.

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

It is not a de Polignac number, because 81611571 - 2⁶ = 81611507 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81611501) 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, 13601926 + ... + 13601931.

It is an arithmetic number, because the mean of its divisors is an integer number (27203858).

Almost surely, 2^81611571 is an apocalyptic number.

81611571 is a deficient number, since it is larger than the sum of its proper divisors (27203861).

81611571 is a wasteful number, since it uses less digits than its factorization.

81611571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27203860.

The product of its digits is 1680, while the sum is 30.

The square root of 81611571 is about 9033.9122754209. The cubic root of 81611571 is about 433.7610777650.

The spelling of 81611571 in words is "eighty-one million, six hundred eleven thousand, five hundred seventy-one".