13123721 has 8 divisors (see below), whose sum is σ = 14327880. Its totient is φ = 11947392.

The previous prime is 13123697. The next prime is 13123727. The reversal of 13123721 is 12732131.

It can be written as a sum of positive squares in 4 ways, for example, as 19321 + 13104400 = 139^2 + 3620^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 13123721 - 2¹⁴ = 13107337 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 13123693 and 13123702.

It is not an unprimeable number, because it can be changed into a prime (13123727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5966 + ... + 7863.

It is an arithmetic number, because the mean of its divisors is an integer number (1790985).

Almost surely, 2^13123721 is an apocalyptic number.

It is an amenable number.

13123721 is a deficient number, since it is larger than the sum of its proper divisors (1204159).

13123721 is a wasteful number, since it uses less digits than its factorization.

13123721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13915.

The product of its digits is 252, while the sum is 20.

The square root of 13123721 is about 3622.6676634767. The cubic root of 13123721 is about 235.8770366328.

Adding to 13123721 its reverse (12732131), we get a palindrome (25855852).

The spelling of 13123721 in words is "thirteen million, one hundred twenty-three thousand, seven hundred twenty-one".