21220393 has 2 divisors, whose sum is σ = 21220394. Its totient is φ = 21220392.

The previous prime is 21220391. The next prime is 21220417. The reversal of 21220393 is 39302212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20820969 + 399424 = 4563^2 + 632^2 .

It is a cyclic number.

It is not a de Polignac number, because 21220393 - 2¹ = 21220391 is a prime.

Together with 21220391, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21220391) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610196 + 10610197.

It is an arithmetic number, because the mean of its divisors is an integer number (10610197).

Almost surely, 2^21220393 is an apocalyptic number.

It is an amenable number.

21220393 is a deficient number, since it is larger than the sum of its proper divisors (1).

21220393 is an equidigital number, since it uses as much as digits as its factorization.

21220393 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 648, while the sum is 22.

The square root of 21220393 is about 4606.5597792713. The cubic root of 21220393 is about 276.8542156672.

The spelling of 21220393 in words is "twenty-one million, two hundred twenty thousand, three hundred ninety-three".