81206138 has 16 divisors (see below), whose sum is σ = 131388936. Its totient is φ = 37419840.

The previous prime is 81206137. The next prime is 81206141. The reversal of 81206138 is 83160218.

It can be written as a sum of positive squares in 4 ways, for example, as 81126049 + 80089 = 9007^2 + 283^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 81206138.

It is not an unprimeable number, because it can be changed into a prime (81206131) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16928 + ... + 21188.

Almost surely, 2^81206138 is an apocalyptic number.

81206138 is a deficient number, since it is larger than the sum of its proper divisors (50182798).

81206138 is a wasteful number, since it uses less digits than its factorization.

81206138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5009.

The product of its (nonzero) digits is 2304, while the sum is 29.

The square root of 81206138 is about 9011.4448342094. Note that the first 3 decimals coincide. The cubic root of 81206138 is about 433.0416002217.

The spelling of 81206138 in words is "eighty-one million, two hundred six thousand, one hundred thirty-eight".