81287636 has 6 divisors (see below), whose sum is σ = 142253370. Its totient is φ = 40643816.

The previous prime is 81287593. The next prime is 81287641. The reversal of 81287636 is 63678218.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 59197636 + 22090000 = 7694^2 + 4700^2 .

It is a junction number, because it is equal to n+sod(n) for n = 81287593 and 81287602.

It is a congruent number.

It is an unprimeable number.

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, 10160951 + ... + 10160958.

It is an arithmetic number, because the mean of its divisors is an integer number (23708895).

Almost surely, 2^81287636 is an apocalyptic number.

It is an amenable number.

81287636 is a deficient number, since it is larger than the sum of its proper divisors (60965734).

81287636 is a wasteful number, since it uses less digits than its factorization.

81287636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20321913 (or 20321911 counting only the distinct ones).

The product of its digits is 96768, while the sum is 41.

The square root of 81287636 is about 9015.9656166159. The cubic root of 81287636 is about 433.1864177831.

The spelling of 81287636 in words is "eighty-one million, two hundred eighty-seven thousand, six hundred thirty-six".