21085853 has 2 divisors, whose sum is σ = 21085854. Its totient is φ = 21085852.

The previous prime is 21085847. The next prime is 21085879. The reversal of 21085853 is 35858012.

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., 19377604 + 1708249 = 4402^2 + 1307^2 .

It is a cyclic number.

It is not a de Polignac number, because 21085853 - 2⁴ = 21085837 is a prime.

It is a super-2 number, since 2×21085853² = 889226393475218, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21085453) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10542926 + 10542927.

It is an arithmetic number, because the mean of its divisors is an integer number (10542927).

Almost surely, 2^21085853 is an apocalyptic number.

It is an amenable number.

21085853 is a deficient number, since it is larger than the sum of its proper divisors (1).

21085853 is an equidigital number, since it uses as much as digits as its factorization.

21085853 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9600, while the sum is 32.

The square root of 21085853 is about 4591.9334707724. The cubic root of 21085853 is about 276.2678777426.

The spelling of 21085853 in words is "twenty-one million, eighty-five thousand, eight hundred fifty-three".