13684721 has 4 divisors (see below), whose sum is σ = 13723200. Its totient is φ = 13646244.

The previous prime is 13684717. The next prime is 13684739. The reversal of 13684721 is 12748631.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12748631 = 7 ⋅1821233.

It is a cyclic number.

It is not a de Polignac number, because 13684721 - 2² = 13684717 is a prime.

It is a super-3 number, since 3×13684721³ (a number of 22 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (13684421) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18701 + ... + 19418.

It is an arithmetic number, because the mean of its divisors is an integer number (3430800).

Almost surely, 2^13684721 is an apocalyptic number.

It is an amenable number.

13684721 is a deficient number, since it is larger than the sum of its proper divisors (38479).

13684721 is an equidigital number, since it uses as much as digits as its factorization.

13684721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38478.

The product of its digits is 8064, while the sum is 32.

The square root of 13684721 is about 3699.2865528369. The cubic root of 13684721 is about 239.1912651124.

The spelling of 13684721 in words is "thirteen million, six hundred eighty-four thousand, seven hundred twenty-one".