21685133 has 2 divisors, whose sum is σ = 21685134. Its totient is φ = 21685132.

The previous prime is 21685129. The next prime is 21685163. The reversal of 21685133 is 33158612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11812969 + 9872164 = 3437^2 + 3142^2 .

It is a cyclic number.

It is not a de Polignac number, because 21685133 - 2² = 21685129 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21685096 and 21685105.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21685163) 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 as a sum of consecutive naturals, namely, 10842566 + 10842567.

It is an arithmetic number, because the mean of its divisors is an integer number (10842567).

Almost surely, 2^21685133 is an apocalyptic number.

It is an amenable number.

21685133 is a deficient number, since it is larger than the sum of its proper divisors (1).

21685133 is an equidigital number, since it uses as much as digits as its factorization.

21685133 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 29.

The square root of 21685133 is about 4656.7298611794. The cubic root of 21685133 is about 278.8607322133.

The spelling of 21685133 in words is "twenty-one million, six hundred eighty-five thousand, one hundred thirty-three".