15968021 has 2 divisors, whose sum is σ = 15968022. Its totient is φ = 15968020.

The previous prime is 15968011. The next prime is 15968023. The reversal of 15968021 is 12086951.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13060996 + 2907025 = 3614^2 + 1705^2 .

It is an emirp because it is prime and its reverse (12086951) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 15968021 - 2¹⁰ = 15966997 is a prime.

It is a Sophie Germain prime.

Together with 15968023, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15968023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7984010 + 7984011.

It is an arithmetic number, because the mean of its divisors is an integer number (7984011).

Almost surely, 2^15968021 is an apocalyptic number.

It is an amenable number.

15968021 is a deficient number, since it is larger than the sum of its proper divisors (1).

15968021 is an equidigital number, since it uses as much as digits as its factorization.

15968021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4320, while the sum is 32.

The square root of 15968021 is about 3996.0006256256. Note that the first 3 decimals coincide. The cubic root of 15968021 is about 251.8162187783.

The spelling of 15968021 in words is "fifteen million, nine hundred sixty-eight thousand, twenty-one".