81128737 has 4 divisors (see below), whose sum is σ = 81540756. Its totient is φ = 80716720.

The previous prime is 81128699. The next prime is 81128779. The reversal of 81128737 is 73782118.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 68161536 + 12967201 = 8256^2 + 3601^2 .

It is a cyclic number.

It is not a de Polignac number, because 81128737 - 2⁷ = 81128609 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81128696 and 81128705.

It is not an unprimeable number, because it can be changed into a prime (81128137) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 205714 + ... + 206107.

It is an arithmetic number, because the mean of its divisors is an integer number (20385189).

Almost surely, 2^81128737 is an apocalyptic number.

It is an amenable number.

81128737 is a deficient number, since it is larger than the sum of its proper divisors (412019).

81128737 is a wasteful number, since it uses less digits than its factorization.

81128737 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 412018.

The product of its digits is 18816, while the sum is 37.

The square root of 81128737 is about 9007.1492160394. The cubic root of 81128737 is about 432.9039730732.

The spelling of 81128737 in words is "eighty-one million, one hundred twenty-eight thousand, seven hundred thirty-seven".