81688340 has 24 divisors (see below), whose sum is σ = 173964672. Its totient is φ = 32214560.

The previous prime is 81688339. The next prime is 81688357. The reversal of 81688340 is 4388618.

It is a junction number, because it is equal to n+sod(n) for n = 81688294 and 81688303.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27344 + ... + 30183.

It is an arithmetic number, because the mean of its divisors is an integer number (7248528).

Almost surely, 2^81688340 is an apocalyptic number.

It is an amenable number.

81688340 is an abundant number, since it is smaller than the sum of its proper divisors (92276332).

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

81688340 is a wasteful number, since it uses less digits than its factorization.

81688340 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57607 (or 57605 counting only the distinct ones).

The product of its (nonzero) digits is 36864, while the sum is 38.

The square root of 81688340 is about 9038.1602110164. The cubic root of 81688340 is about 433.8970428332.

It can be divided in two parts, 81688 and 340, that added together give a palindrome (82028).

The spelling of 81688340 in words is "eighty-one million, six hundred eighty-eight thousand, three hundred forty".