21424553 has 4 divisors (see below), whose sum is σ = 21518340. Its totient is φ = 21330768.

The previous prime is 21424549. The next prime is 21424577. The reversal of 21424553 is 35542412.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13601344 + 7823209 = 3688^2 + 2797^2 .

It is a cyclic number.

It is not a de Polignac number, because 21424553 - 2² = 21424549 is a prime.

It is a super-2 number, since 2×21424553² = 918022942499618, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21424253) 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 in 3 ways as a sum of consecutive naturals, for example, 46550 + ... + 47007.

It is an arithmetic number, because the mean of its divisors is an integer number (5379585).

Almost surely, 2^21424553 is an apocalyptic number.

It is an amenable number.

21424553 is a deficient number, since it is larger than the sum of its proper divisors (93787).

21424553 is an equidigital number, since it uses as much as digits as its factorization.

21424553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 93786.

The product of its digits is 4800, while the sum is 26.

The square root of 21424553 is about 4628.6664386192. Note that the first 3 decimals coincide. The cubic root of 21424553 is about 277.7392488013.

Adding to 21424553 its reverse (35542412), we get a palindrome (56966965).

The spelling of 21424553 in words is "twenty-one million, four hundred twenty-four thousand, five hundred fifty-three".