81616571 has 4 divisors (see below), whose sum is σ = 85912200. Its totient is φ = 77320944.

The previous prime is 81616553. The next prime is 81616589. The reversal of 81616571 is 17561618.

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

It is an interprime number because it is at equal distance from previous prime (81616553) and next prime (81616589).

It is a cyclic number.

It is not a de Polignac number, because 81616571 - 2²⁶ = 14507707 is a prime.

It is a super-2 number, since 2×81616571² = 13322529323596082, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81616501) 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, 2147786 + ... + 2147823.

It is an arithmetic number, because the mean of its divisors is an integer number (21478050).

Almost surely, 2^81616571 is an apocalyptic number.

81616571 is a deficient number, since it is larger than the sum of its proper divisors (4295629).

81616571 is a wasteful number, since it uses less digits than its factorization.

81616571 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4295628.

The product of its digits is 10080, while the sum is 35.

The square root of 81616571 is about 9034.1890062141. The cubic root of 81616571 is about 433.7699358271.

The spelling of 81616571 in words is "eighty-one million, six hundred sixteen thousand, five hundred seventy-one".