21000053 has 4 divisors (see below), whose sum is σ = 21567660. Its totient is φ = 20432448.

The previous prime is 21000041. The next prime is 21000059. The reversal of 21000053 is 35000012.

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 18992164 + 2007889 = 4358^2 + 1417^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000053 - 2⁴ = 21000037 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 20999998 and 21000043.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000059) 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, 283748 + ... + 283821.

It is an arithmetic number, because the mean of its divisors is an integer number (5391915).

Almost surely, 2^21000053 is an apocalyptic number.

It is an amenable number.

21000053 is a deficient number, since it is larger than the sum of its proper divisors (567607).

21000053 is an equidigital number, since it uses as much as digits as its factorization.

21000053 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 567606.

The product of its (nonzero) digits is 30, while the sum is 11.

The square root of 21000053 is about 4582.5814777263. The cubic root of 21000053 is about 275.8926497379.

Adding to 21000053 its reverse (35000012), we get a palindrome (56000065).

The spelling of 21000053 in words is "twenty-one million, fifty-three", and thus it is an aban number and an uban number.