81209908 has 24 divisors (see below), whose sum is σ = 153971720. Its totient is φ = 37477440.

The previous prime is 81209893. The next prime is 81209911. The reversal of 81209908 is 80990218.

It can be written as a sum of positive squares in 4 ways, for example, as 4787344 + 76422564 = 2188^2 + 8742^2 .

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 in 7 ways as a sum of consecutive naturals, for example, 4168 + ... + 13408.

Almost surely, 2^81209908 is an apocalyptic number.

It is an amenable number.

81209908 is a deficient number, since it is larger than the sum of its proper divisors (72761812).

81209908 is a wasteful number, since it uses less digits than its factorization.

81209908 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9284 (or 9256 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 37.

The square root of 81209908 is about 9011.6540102248. The cubic root of 81209908 is about 433.0483014457.

The spelling of 81209908 in words is "eighty-one million, two hundred nine thousand, nine hundred eight".