13091721 has 8 divisors (see below), whose sum is σ = 17628864. Its totient is φ = 8641200.

The previous prime is 13091699. The next prime is 13091723. The reversal of 13091721 is 12719031.

13091721 is digitally balanced in base 2 and base 3, because in such bases it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 13091721 - 2⁷ = 13091593 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 13091691 and 13091700.

It is not an unprimeable number, because it can be changed into a prime (13091723) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21301 + ... + 21906.

It is an arithmetic number, because the mean of its divisors is an integer number (2203608).

Almost surely, 2^13091721 is an apocalyptic number.

It is an amenable number.

13091721 is a deficient number, since it is larger than the sum of its proper divisors (4537143).

13091721 is a wasteful number, since it uses less digits than its factorization.

13091721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43311.

The product of its (nonzero) digits is 378, while the sum is 24.

The square root of 13091721 is about 3618.2483331026. The cubic root of 13091721 is about 235.6851650238.

The spelling of 13091721 in words is "thirteen million, ninety-one thousand, seven hundred twenty-one".