15243721 has 2 divisors, whose sum is σ = 15243722. Its totient is φ = 15243720.

The previous prime is 15243703. The next prime is 15243727. The reversal of 15243721 is 12734251.

It is a happy number.

15243721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14907321 + 336400 = 3861^2 + 580^2 .

It is a cyclic number.

It is not a de Polignac number, because 15243721 - 2⁵ = 15243689 is a prime.

It is not a weakly prime, because it can be changed into another prime (15243727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7621860 + 7621861.

It is an arithmetic number, because the mean of its divisors is an integer number (7621861).

Almost surely, 2^15243721 is an apocalyptic number.

It is an amenable number.

15243721 is a deficient number, since it is larger than the sum of its proper divisors (1).

15243721 is an equidigital number, since it uses as much as digits as its factorization.

15243721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1680, while the sum is 25.

The square root of 15243721 is about 3904.3208116137. The cubic root of 15243721 is about 247.9497437620.

Adding to 15243721 its reverse (12734251), we get a palindrome (27977972).

The spelling of 15243721 in words is "fifteen million, two hundred forty-three thousand, seven hundred twenty-one".