16388921 has 2 divisors, whose sum is σ = 16388922. Its totient is φ = 16388920.

The previous prime is 16388917. The next prime is 16388923. The reversal of 16388921 is 12988361.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16362025 + 26896 = 4045^2 + 164^2 .

It is an emirp because it is prime and its reverse (12988361) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 16388921 - 2² = 16388917 is a prime.

Together with 16388923, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (16388923) 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, 8194460 + 8194461.

It is an arithmetic number, because the mean of its divisors is an integer number (8194461).

Almost surely, 2^16388921 is an apocalyptic number.

It is an amenable number.

16388921 is a deficient number, since it is larger than the sum of its proper divisors (1).

16388921 is an equidigital number, since it uses as much as digits as its factorization.

16388921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20736, while the sum is 38.

The square root of 16388921 is about 4048.3232331423. The cubic root of 16388921 is about 254.0095941568.

The spelling of 16388921 in words is "sixteen million, three hundred eighty-eight thousand, nine hundred twenty-one".