81605136 has 20 divisors (see below), whose sum is σ = 210813392. Its totient is φ = 27201696.

The previous prime is 81605131. The next prime is 81605137. The reversal of 81605136 is 63150618.

It is not an unprimeable number, because it can be changed into a prime (81605131) 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 3 ways as a sum of consecutive naturals, for example, 850006 + ... + 850101.

Almost surely, 2^81605136 is an apocalyptic number.

It is an amenable number.

81605136 is an abundant number, since it is smaller than the sum of its proper divisors (129208256).

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

81605136 is a wasteful number, since it uses less digits than its factorization.

81605136 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1700118 (or 1700112 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 30.

The square root of 81605136 is about 9033.5561104141. The cubic root of 81605136 is about 433.7496769065.

The spelling of 81605136 in words is "eighty-one million, six hundred five thousand, one hundred thirty-six".