81617775 has 12 divisors (see below), whose sum is σ = 134941512. Its totient is φ = 43529440.

The previous prime is 81617771. The next prime is 81617821. The reversal of 81617775 is 57771618.

It is not a de Polignac number, because 81617775 - 2² = 81617771 is a prime.

It is a super-2 number, since 2×81617775² = 13322922391901250, which contains 22 as substring.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81617771) 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 11 ways as a sum of consecutive naturals, for example, 544044 + ... + 544193.

It is an arithmetic number, because the mean of its divisors is an integer number (11245126).

Almost surely, 2^81617775 is an apocalyptic number.

81617775 is a deficient number, since it is larger than the sum of its proper divisors (53323737).

81617775 is a wasteful number, since it uses less digits than its factorization.

81617775 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1088250 (or 1088245 counting only the distinct ones).

The product of its digits is 82320, while the sum is 42.

The square root of 81617775 is about 9034.2556417228. The cubic root of 81617775 is about 433.7720687944.

The spelling of 81617775 in words is "eighty-one million, six hundred seventeen thousand, seven hundred seventy-five".