21144553 has 2 divisors, whose sum is σ = 21144554. Its totient is φ = 21144552.

The previous prime is 21144551. The next prime is 21144559. The reversal of 21144553 is 35544112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11854249 + 9290304 = 3443^2 + 3048^2 .

It is a cyclic number.

It is not a de Polignac number, because 21144553 - 2¹ = 21144551 is a prime.

Together with 21144551, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21144551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10572276 + 10572277.

It is an arithmetic number, because the mean of its divisors is an integer number (10572277).

Almost surely, 2^21144553 is an apocalyptic number.

It is an amenable number.

21144553 is a deficient number, since it is larger than the sum of its proper divisors (1).

21144553 is an equidigital number, since it uses as much as digits as its factorization.

21144553 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2400, while the sum is 25.

The square root of 21144553 is about 4598.3206717235. The cubic root of 21144553 is about 276.5240036408.

Adding to 21144553 its reverse (35544112), we get a palindrome (56688665).

The spelling of 21144553 in words is "twenty-one million, one hundred forty-four thousand, five hundred fifty-three".