81685990 has 8 divisors (see below), whose sum is σ = 147034800. Its totient is φ = 32674392.

The previous prime is 81685963. The next prime is 81685999. The reversal of 81685990 is 9958618.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a self number, because there is not a number n which added to its sum of digits gives 81685990.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81685999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4084290 + ... + 4084309.

It is an arithmetic number, because the mean of its divisors is an integer number (18379350).

Almost surely, 2^81685990 is an apocalyptic number.

81685990 is a deficient number, since it is larger than the sum of its proper divisors (65348810).

81685990 is a wasteful number, since it uses less digits than its factorization.

81685990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8168606.

The product of its (nonzero) digits is 155520, while the sum is 46.

The square root of 81685990 is about 9038.0302057473. The cubic root of 81685990 is about 433.8928820279.

The spelling of 81685990 in words is "eighty-one million, six hundred eighty-five thousand, nine hundred ninety".