13666921 has 4 divisors (see below), whose sum is σ = 13840000. Its totient is φ = 13493844.

The previous prime is 13666889. The next prime is 13666927. The reversal of 13666921 is 12966631.

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: 12966631 = 17 ⋅762743.

It is a cyclic number.

It is not a de Polignac number, because 13666921 - 2⁵ = 13666889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (13666927) 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, 86421 + ... + 86578.

It is an arithmetic number, because the mean of its divisors is an integer number (3460000).

Almost surely, 2^13666921 is an apocalyptic number.

It is an amenable number.

13666921 is a deficient number, since it is larger than the sum of its proper divisors (173079).

13666921 is an equidigital number, since it uses as much as digits as its factorization.

13666921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173078.

The product of its digits is 11664, while the sum is 34.

The square root of 13666921 is about 3696.8799006730. The cubic root of 13666921 is about 239.0875131047.

The spelling of 13666921 in words is "thirteen million, six hundred sixty-six thousand, nine hundred twenty-one".