21243355 has 16 divisors (see below), whose sum is σ = 29571840. Its totient is φ = 14347872.

The previous prime is 21243347. The next prime is 21243359. The reversal of 21243355 is 55334212.

It is not a de Polignac number, because 21243355 - 2³ = 21243347 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21243359) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2185 + ... + 6874.

It is an arithmetic number, because the mean of its divisors is an integer number (1848240).

Almost surely, 2^21243355 is an apocalyptic number.

21243355 is a deficient number, since it is larger than the sum of its proper divisors (8328485).

21243355 is an equidigital number, since it uses as much as digits as its factorization.

21243355 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9138.

The product of its digits is 3600, while the sum is 25.

The square root of 21243355 is about 4609.0514208457. The cubic root of 21243355 is about 276.9540384324.

Adding to 21243355 its reverse (55334212), we get a palindrome (76577567).

The spelling of 21243355 in words is "twenty-one million, two hundred forty-three thousand, three hundred fifty-five".