81691936 has 24 divisors (see below), whose sum is σ = 170292780. Its totient is φ = 38443008.

The previous prime is 81691933. The next prime is 81691937. The reversal of 81691936 is 63919618.

It can be written as a sum of positive squares in 2 ways, for example, as 63680400 + 18011536 = 7980^2 + 4244^2 .

It is a junction number, because it is equal to n+sod(n) for n = 81691892 and 81691901.

It is not an unprimeable number, because it can be changed into a prime (81691933) 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, 74541 + ... + 75628.

Almost surely, 2^81691936 is an apocalyptic number.

It is an amenable number.

81691936 is an abundant number, since it is smaller than the sum of its proper divisors (88600844).

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

81691936 is a wasteful number, since it uses less digits than its factorization.

81691936 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 150196 (or 150188 counting only the distinct ones).

The product of its digits is 69984, while the sum is 43.

The square root of 81691936 is about 9038.3591431188. The cubic root of 81691936 is about 433.9034095961.

The spelling of 81691936 in words is "eighty-one million, six hundred ninety-one thousand, nine hundred thirty-six".