21103553 has 2 divisors, whose sum is σ = 21103554. Its totient is φ = 21103552.

The previous prime is 21103549. The next prime is 21103559. The reversal of 21103553 is 35530112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12623809 + 8479744 = 3553^2 + 2912^2 .

It is a cyclic number.

It is not a de Polignac number, because 21103553 - 2² = 21103549 is a prime.

It is not a weakly prime, because it can be changed into another prime (21103559) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10551776 + 10551777.

It is an arithmetic number, because the mean of its divisors is an integer number (10551777).

Almost surely, 2^21103553 is an apocalyptic number.

It is an amenable number.

21103553 is a deficient number, since it is larger than the sum of its proper divisors (1).

21103553 is an equidigital number, since it uses as much as digits as its factorization.

21103553 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 450, while the sum is 20.

The square root of 21103553 is about 4593.8603592186. The cubic root of 21103553 is about 276.3451582116.

Adding to 21103553 its reverse (35530112), we get a palindrome (56633665).

The spelling of 21103553 in words is "twenty-one million, one hundred three thousand, five hundred fifty-three".