81616569 has 4 divisors (see below), whose sum is σ = 108822096. Its totient is φ = 54411044.

The previous prime is 81616553. The next prime is 81616589. The reversal of 81616569 is 96561618.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81616569 - 2⁴ = 81616553 is a prime.

It is a super-4 number, since 4×81616569⁴ (a number of 33 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is an alternating number because its digits alternate between even and odd.

It is a self number, because there is not a number n which added to its sum of digits gives 81616569.

It is not an unprimeable number, because it can be changed into a prime (81616589) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13602759 + ... + 13602764.

It is an arithmetic number, because the mean of its divisors is an integer number (27205524).

Almost surely, 2^81616569 is an apocalyptic number.

It is an amenable number.

81616569 is a deficient number, since it is larger than the sum of its proper divisors (27205527).

81616569 is a wasteful number, since it uses less digits than its factorization.

81616569 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27205526.

The product of its digits is 77760, while the sum is 42.

The square root of 81616569 is about 9034.1888955235. The cubic root of 81616569 is about 433.7699322839.

The spelling of 81616569 in words is "eighty-one million, six hundred sixteen thousand, five hundred sixty-nine".