13387721 has 4 divisors (see below), whose sum is σ = 14175252. Its totient is φ = 12600192.

The previous prime is 13387711. The next prime is 13387727. The reversal of 13387721 is 12778331.

13387721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 3553225 + 9834496 = 1885^2 + 3136^2 .

It is a cyclic number.

It is not a de Polignac number, because 13387721 - 2²² = 9193417 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (13387727) 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, 393740 + ... + 393773.

It is an arithmetic number, because the mean of its divisors is an integer number (3543813).

Almost surely, 2^13387721 is an apocalyptic number.

It is an amenable number.

13387721 is a deficient number, since it is larger than the sum of its proper divisors (787531).

13387721 is an equidigital number, since it uses as much as digits as its factorization.

13387721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 787530.

The product of its digits is 7056, while the sum is 32.

The square root of 13387721 is about 3658.9234755594. The cubic root of 13387721 is about 237.4482014460.

The spelling of 13387721 in words is "thirteen million, three hundred eighty-seven thousand, seven hundred twenty-one".