21000853 has 2 divisors, whose sum is σ = 21000854. Its totient is φ = 21000852.

The previous prime is 21000851. The next prime is 21000883. The reversal of 21000853 is 35800012.

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., 15350724 + 5650129 = 3918^2 + 2377^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000853 - 2¹ = 21000851 is a prime.

Together with 21000851, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21000853.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21000851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500426 + 10500427.

It is an arithmetic number, because the mean of its divisors is an integer number (10500427).

Almost surely, 2^21000853 is an apocalyptic number.

It is an amenable number.

21000853 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000853 is an equidigital number, since it uses as much as digits as its factorization.

21000853 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 21000853 is about 4582.6687639409. The cubic root of 21000853 is about 275.8961530833.

Adding to 21000853 its reverse (35800012), we get a palindrome (56800865).

The spelling of 21000853 in words is "twenty-one million, eight hundred fifty-three", and thus it is an aban number.