13666621 has 4 divisors (see below), whose sum is σ = 13807612. Its totient is φ = 13525632.

The previous prime is 13666607. The next prime is 13666661. The reversal of 13666621 is 12666631.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10169721 + 3496900 = 3189^2 + 1870^2 .

It is a cyclic number.

It is not a de Polignac number, because 13666621 - 2⁷ = 13666493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (13666661) 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 3 ways as a sum of consecutive naturals, for example, 70350 + ... + 70543.

It is an arithmetic number, because the mean of its divisors is an integer number (3451903).

Almost surely, 2^13666621 is an apocalyptic number.

It is an amenable number.

13666621 is a deficient number, since it is larger than the sum of its proper divisors (140991).

13666621 is an equidigital number, since it uses as much as digits as its factorization.

13666621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 140990.

The product of its digits is 7776, while the sum is 31.

The square root of 13666621 is about 3696.8393256943. The cubic root of 13666621 is about 239.0857637036.

The spelling of 13666621 in words is "thirteen million, six hundred sixty-six thousand, six hundred twenty-one".