81616065 has 16 divisors (see below), whose sum is σ = 138267648. Its totient is φ = 40967936.

The previous prime is 81616061. The next prime is 81616097. The reversal of 81616065 is 56061618.

It is a cyclic number.

It is not a de Polignac number, because 81616065 - 2² = 81616061 is a prime.

It is a super-2 number, since 2×81616065² = 13322364132168450, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81616061) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 159777 + ... + 160286.

It is an arithmetic number, because the mean of its divisors is an integer number (8641728).

Almost surely, 2^81616065 is an apocalyptic number.

81616065 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

It is an amenable number.

81616065 is a deficient number, since it is larger than the sum of its proper divisors (56651583).

81616065 is a wasteful number, since it uses less digits than its factorization.

81616065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320088.

The product of its (nonzero) digits is 8640, while the sum is 33.

The square root of 81616065 is about 9034.1610014434. The cubic root of 81616065 is about 433.7690394076.

The spelling of 81616065 in words is "eighty-one million, six hundred sixteen thousand, sixty-five".