13081721 has 16 divisors (see below), whose sum is σ = 14496768. Its totient is φ = 11750400.

The previous prime is 13081699. The next prime is 13081727. The reversal of 13081721 is 12718031.

It is a happy number.

It is not a de Polignac number, because 13081721 - 2¹⁴ = 13065337 is a prime.

It is a super-2 number, since 2×13081721² = 342262848643682, which contains 22 as substring.

It is a Smith number, since the sum of its digits (23) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (13081727) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 54161 + ... + 54401.

It is an arithmetic number, because the mean of its divisors is an integer number (906048).

Almost surely, 2^13081721 is an apocalyptic number.

It is an amenable number.

13081721 is a deficient number, since it is larger than the sum of its proper divisors (1415047).

13081721 is a wasteful number, since it uses less digits than its factorization.

13081721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 392.

The product of its (nonzero) digits is 336, while the sum is 23.

The square root of 13081721 is about 3616.8661849728. The cubic root of 13081721 is about 235.6251410338.

Adding to 13081721 its reverse (12718031), we get a palindrome (25799752).

The spelling of 13081721 in words is "thirteen million, eighty-one thousand, seven hundred twenty-one".