15724921 has 2 divisors, whose sum is σ = 15724922. Its totient is φ = 15724920.

The previous prime is 15724909. The next prime is 15724927. The reversal of 15724921 is 12942751.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14714896 + 1010025 = 3836^2 + 1005^2 .

It is an emirp because it is prime and its reverse (12942751) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 15724921 - 2¹¹ = 15722873 is a prime.

It is not a weakly prime, because it can be changed into another prime (15724927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7862460 + 7862461.

It is an arithmetic number, because the mean of its divisors is an integer number (7862461).

Almost surely, 2^15724921 is an apocalyptic number.

It is an amenable number.

15724921 is a deficient number, since it is larger than the sum of its proper divisors (1).

15724921 is an equidigital number, since it uses as much as digits as its factorization.

15724921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5040, while the sum is 31.

The square root of 15724921 is about 3965.4660507940. The cubic root of 15724921 is about 250.5317800379.

The spelling of 15724921 in words is "fifteen million, seven hundred twenty-four thousand, nine hundred twenty-one".