81440168 has 8 divisors (see below), whose sum is σ = 152700330. Its totient is φ = 40720080.

The previous prime is 81440159. The next prime is 81440173. The reversal of 81440168 is 86104418.

It can be written as a sum of positive squares in only one way, i.e., 58033924 + 23406244 = 7618^2 + 4838^2 .

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

It is a plaindrome in base 12.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5090003 + ... + 5090018.

Almost surely, 2^81440168 is an apocalyptic number.

It is an amenable number.

81440168 is a deficient number, since it is larger than the sum of its proper divisors (71260162).

81440168 is a wasteful number, since it uses less digits than its factorization.

81440168 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10180027 (or 10180023 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 32.

The square root of 81440168 is about 9024.4206462243. The cubic root of 81440168 is about 433.4571990414.

The spelling of 81440168 in words is "eighty-one million, four hundred forty thousand, one hundred sixty-eight".