21817853 has 2 divisors, whose sum is σ = 21817854. Its totient is φ = 21817852.

The previous prime is 21817849. The next prime is 21817867. The reversal of 21817853 is 35871812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20811844 + 1006009 = 4562^2 + 1003^2 .

It is a cyclic number.

It is not a de Polignac number, because 21817853 - 2² = 21817849 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21817153) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10908926 + 10908927.

It is an arithmetic number, because the mean of its divisors is an integer number (10908927).

Almost surely, 2^21817853 is an apocalyptic number.

It is an amenable number.

21817853 is a deficient number, since it is larger than the sum of its proper divisors (1).

21817853 is an equidigital number, since it uses as much as digits as its factorization.

21817853 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13440, while the sum is 35.

The square root of 21817853 is about 4670.9584669530. The cubic root of 21817853 is about 279.4284813541.

The spelling of 21817853 in words is "twenty-one million, eight hundred seventeen thousand, eight hundred fifty-three".