21685163 has 2 divisors, whose sum is σ = 21685164. Its totient is φ = 21685162.

The previous prime is 21685133. The next prime is 21685171. The reversal of 21685163 is 36158612.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21685163 - 2¹⁸ = 21423019 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21685133) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10842581 + 10842582.

It is an arithmetic number, because the mean of its divisors is an integer number (10842582).

Almost surely, 2^21685163 is an apocalyptic number.

21685163 is a deficient number, since it is larger than the sum of its proper divisors (1).

21685163 is an equidigital number, since it uses as much as digits as its factorization.

21685163 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8640, while the sum is 32.

The square root of 21685163 is about 4656.7330823228. The cubic root of 21685163 is about 278.8608608086.

The spelling of 21685163 in words is "twenty-one million, six hundred eighty-five thousand, one hundred sixty-three".