81937809 has 12 divisors (see below), whose sum is σ = 118560000. Its totient is φ = 54530424.

The previous prime is 81937783. The next prime is 81937811. The reversal of 81937809 is 90873918.

It is not a de Polignac number, because 81937809 - 2⁵ = 81937777 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81937879) 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 11 ways as a sum of consecutive naturals, for example, 2209 + ... + 12990.

It is an arithmetic number, because the mean of its divisors is an integer number (9880000).

Almost surely, 2^81937809 is an apocalyptic number.

It is an amenable number.

81937809 is a deficient number, since it is larger than the sum of its proper divisors (36622191).

81937809 is a wasteful number, since it uses less digits than its factorization.

81937809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15804 (or 15801 counting only the distinct ones).

The product of its (nonzero) digits is 108864, while the sum is 45.

The square root of 81937809 is about 9051.9505632764. The cubic root of 81937809 is about 434.3382884213.

The spelling of 81937809 in words is "eighty-one million, nine hundred thirty-seven thousand, eight hundred nine".