21103513 has 2 divisors, whose sum is σ = 21103514. Its totient is φ = 21103512.

The previous prime is 21103501. The next prime is 21103519. The reversal of 21103513 is 31530112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17405584 + 3697929 = 4172^2 + 1923^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21103513 is a prime.

It is not a weakly prime, because it can be changed into another prime (21103519) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10551756 + 10551757.

It is an arithmetic number, because the mean of its divisors is an integer number (10551757).

Almost surely, 2^21103513 is an apocalyptic number.

It is an amenable number.

21103513 is a deficient number, since it is larger than the sum of its proper divisors (1).

21103513 is an equidigital number, since it uses as much as digits as its factorization.

21103513 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 90, while the sum is 16.

The square root of 21103513 is about 4593.8560055796. The cubic root of 21103513 is about 276.3449836151.

Adding to 21103513 its reverse (31530112), we get a palindrome (52633625).

The spelling of 21103513 in words is "twenty-one million, one hundred three thousand, five hundred thirteen".