21553393 has 2 divisors, whose sum is σ = 21553394. Its totient is φ = 21553392.

The previous prime is 21553379. The next prime is 21553403. The reversal of 21553393 is 39335512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21455424 + 97969 = 4632^2 + 313^2 .

It is a cyclic number.

It is not a de Polignac number, because 21553393 - 2⁵ = 21553361 is a prime.

It is not a weakly prime, because it can be changed into another prime (21593393) 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, 10776696 + 10776697.

It is an arithmetic number, because the mean of its divisors is an integer number (10776697).

Almost surely, 2^21553393 is an apocalyptic number.

It is an amenable number.

21553393 is a deficient number, since it is larger than the sum of its proper divisors (1).

21553393 is an equidigital number, since it uses as much as digits as its factorization.

21553393 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12150, while the sum is 31.

The square root of 21553393 is about 4642.5631928925. The cubic root of 21553393 is about 278.2948797279.

The spelling of 21553393 in words is "twenty-one million, five hundred fifty-three thousand, three hundred ninety-three".