15663421 has 2 divisors, whose sum is σ = 15663422. Its totient is φ = 15663420.

The previous prime is 15663413. The next prime is 15663433. The reversal of 15663421 is 12436651.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9084196 + 6579225 = 3014^2 + 2565^2 .

It is an emirp because it is prime and its reverse (12436651) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 15663421 - 2³ = 15663413 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 15663421.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15663121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7831710 + 7831711.

It is an arithmetic number, because the mean of its divisors is an integer number (7831711).

Almost surely, 2^15663421 is an apocalyptic number.

It is an amenable number.

15663421 is a deficient number, since it is larger than the sum of its proper divisors (1).

15663421 is an equidigital number, since it uses as much as digits as its factorization.

15663421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 28.

The square root of 15663421 is about 3957.7040061126. The cubic root of 15663421 is about 250.2047442734.

The spelling of 15663421 in words is "fifteen million, six hundred sixty-three thousand, four hundred twenty-one".