21919393 has 2 divisors, whose sum is σ = 21919394. Its totient is φ = 21919392.

The previous prime is 21919363. The next prime is 21919397. The reversal of 21919393 is 39391912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21827584 + 91809 = 4672^2 + 303^2 .

It is a cyclic number.

It is not a de Polignac number, because 21919393 - 2⁵ = 21919361 is a prime.

It is not a weakly prime, because it can be changed into another prime (21919397) 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, 10959696 + 10959697.

It is an arithmetic number, because the mean of its divisors is an integer number (10959697).

Almost surely, 2^21919393 is an apocalyptic number.

It is an amenable number.

21919393 is a deficient number, since it is larger than the sum of its proper divisors (1).

21919393 is an equidigital number, since it uses as much as digits as its factorization.

21919393 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13122, while the sum is 37.

The square root of 21919393 is about 4681.8151394518. The cubic root of 21919393 is about 279.8612960974.

The spelling of 21919393 in words is "twenty-one million, nine hundred nineteen thousand, three hundred ninety-three".