81641608 has 8 divisors (see below), whose sum is σ = 153078030. Its totient is φ = 40820800.

The previous prime is 81641603. The next prime is 81641617. The reversal of 81641608 is 80614618.

It can be written as a sum of positive squares in only one way, i.e., 68260644 + 13380964 = 8262^2 + 3658^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (81641603) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5102593 + ... + 5102608.

Almost surely, 2^81641608 is an apocalyptic number.

It is an amenable number.

81641608 is a deficient number, since it is larger than the sum of its proper divisors (71436422).

81641608 is a wasteful number, since it uses less digits than its factorization.

81641608 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10205207 (or 10205203 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 34.

The square root of 81641608 is about 9035.5745805123. The cubic root of 81641608 is about 433.8142862469.

It can be divided in two parts, 816 and 41608, that added together give a palindrome (42424).

The spelling of 81641608 in words is "eighty-one million, six hundred forty-one thousand, six hundred eight".