81684819 has 24 divisors (see below), whose sum is σ = 126556560. Its totient is φ = 50611392.

The previous prime is 81684817. The next prime is 81684839. The reversal of 81684819 is 91848618.

81684819 is a `hidden beast` number, since 8 + 168 + 481 + 9 = 666.

It is not a de Polignac number, because 81684819 - 2¹ = 81684817 is a prime.

It is a super-2 number, since 2×81684819² = 13344819310125522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81684817) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4557 + ... + 13569.

It is an arithmetic number, because the mean of its divisors is an integer number (5273190).

Almost surely, 2^81684819 is an apocalyptic number.

81684819 is a deficient number, since it is larger than the sum of its proper divisors (44871741).

81684819 is a wasteful number, since it uses less digits than its factorization.

81684819 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9091 (or 9088 counting only the distinct ones).

The product of its digits is 110592, while the sum is 45.

The square root of 81684819 is about 9037.9654237002. The cubic root of 81684819 is about 433.8908086777.

The spelling of 81684819 in words is "eighty-one million, six hundred eighty-four thousand, eight hundred nineteen".