81684519 has 12 divisors (see below), whose sum is σ = 126694584. Its totient is φ = 46676784.

The previous prime is 81684517. The next prime is 81684521. The reversal of 81684519 is 91548618.

It is an interprime number because it is at equal distance from previous prime (81684517) and next prime (81684521).

It is not a de Polignac number, because 81684519 - 2¹ = 81684517 is a prime.

It is a super-2 number, since 2×81684519² = 13344721288522722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81684517) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 277692 + ... + 277985.

It is an arithmetic number, because the mean of its divisors is an integer number (10557882).

Almost surely, 2^81684519 is an apocalyptic number.

81684519 is a deficient number, since it is larger than the sum of its proper divisors (45010065).

81684519 is a wasteful number, since it uses less digits than its factorization.

81684519 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 555694 (or 555687 counting only the distinct ones).

The product of its digits is 69120, while the sum is 42.

The square root of 81684519 is about 9037.9488270293. The cubic root of 81684519 is about 433.8902775002.

The spelling of 81684519 in words is "eighty-one million, six hundred eighty-four thousand, five hundred nineteen".