81145138 has 4 divisors (see below), whose sum is σ = 121717710. Its totient is φ = 40572568.

The previous prime is 81145093. The next prime is 81145139. The reversal of 81145138 is 83154118.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 83154118 = 2 ⋅41577059.

It can be written as a sum of positive squares in only one way, i.e., 77915929 + 3229209 = 8827^2 + 1797^2 .

It is not an unprimeable number, because it can be changed into a prime (81145139) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20286283 + ... + 20286286.

Almost surely, 2^81145138 is an apocalyptic number.

81145138 is a deficient number, since it is larger than the sum of its proper divisors (40572572).

81145138 is a wasteful number, since it uses less digits than its factorization.

81145138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40572571.

The product of its digits is 3840, while the sum is 31.

The square root of 81145138 is about 9008.0596134795. The cubic root of 81145138 is about 432.9331430892.

The spelling of 81145138 in words is "eighty-one million, one hundred forty-five thousand, one hundred thirty-eight".