20685971 has 2 divisors, whose sum is σ = 20685972. Its totient is φ = 20685970.

The previous prime is 20685919. The next prime is 20685983. The reversal of 20685971 is 17958602.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20685971 - 2¹⁰ = 20684947 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (20685571) 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, 10342985 + 10342986.

It is an arithmetic number, because the mean of its divisors is an integer number (10342986).

Almost surely, 2^20685971 is an apocalyptic number.

20685971 is a deficient number, since it is larger than the sum of its proper divisors (1).

20685971 is an equidigital number, since it uses as much as digits as its factorization.

20685971 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 30240, while the sum is 38.

The square root of 20685971 is about 4548.1832636779. The cubic root of 20685971 is about 274.5102954213.

The spelling of 20685971 in words is "twenty million, six hundred eighty-five thousand, nine hundred seventy-one".