81636140 has 24 divisors (see below), whose sum is σ = 173365920. Its totient is φ = 32286848.

The previous prime is 81636109. The next prime is 81636143. The reversal of 81636140 is 4163618.

It is not an unprimeable number, because it can be changed into a prime (81636143) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21152 + ... + 24711.

It is an arithmetic number, because the mean of its divisors is an integer number (7223580).

Almost surely, 2^81636140 is an apocalyptic number.

It is an amenable number.

81636140 is an abundant number, since it is smaller than the sum of its proper divisors (91729780).

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

81636140 is a wasteful number, since it uses less digits than its factorization.

81636140 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45961 (or 45959 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 81636140 is about 9035.2719936923. The cubic root of 81636140 is about 433.8046010323.

Adding to 81636140 its reverse (4163618), we get a palindrome (85799758).

The spelling of 81636140 in words is "eighty-one million, six hundred thirty-six thousand, one hundred forty".