81609768 has 40 divisors (see below), whose sum is σ = 228584730. Its totient is φ = 27203040.

The previous prime is 81609767. The next prime is 81609779. The reversal of 81609768 is 86790618.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 46539684 + 35070084 = 6822^2 + 5922^2 .

It is not an unprimeable number, because it can be changed into a prime (81609761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 62323 + ... + 63618.

Almost surely, 2^81609768 is an apocalyptic number.

It is an amenable number.

81609768 is an abundant number, since it is smaller than the sum of its proper divisors (146974962).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81609768 is a wasteful number, since it uses less digits than its factorization.

81609768 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 125959 (or 125946 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 45.

The square root of 81609768 is about 9033.8124842173. The cubic root of 81609768 is about 433.7578834590.

The spelling of 81609768 in words is "eighty-one million, six hundred nine thousand, seven hundred sixty-eight".