21045553 has 2 divisors, whose sum is σ = 21045554. Its totient is φ = 21045552.

The previous prime is 21045547. The next prime is 21045593. The reversal of 21045553 is 35554012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20866624 + 178929 = 4568^2 + 423^2 .

It is a cyclic number.

It is not a de Polignac number, because 21045553 - 2⁹ = 21045041 is a prime.

It is not a weakly prime, because it can be changed into another prime (21045593) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10522776 + 10522777.

It is an arithmetic number, because the mean of its divisors is an integer number (10522777).

Almost surely, 2^21045553 is an apocalyptic number.

It is an amenable number.

21045553 is a deficient number, since it is larger than the sum of its proper divisors (1).

21045553 is an equidigital number, since it uses as much as digits as its factorization.

21045553 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3000, while the sum is 25.

The square root of 21045553 is about 4587.5432423030. The cubic root of 21045553 is about 276.0917613043.

Adding to 21045553 its reverse (35554012), we get a palindrome (56599565).

The spelling of 21045553 in words is "twenty-one million, forty-five thousand, five hundred fifty-three".