20871689 has 2 divisors, whose sum is σ = 20871690. Its totient is φ = 20871688.

The previous prime is 20871667. The next prime is 20871691. The reversal of 20871689 is 98617802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20097289 + 774400 = 4483^2 + 880^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20871689 is a prime.

Together with 20871691, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20871629) 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, 10435844 + 10435845.

It is an arithmetic number, because the mean of its divisors is an integer number (10435845).

Almost surely, 2^20871689 is an apocalyptic number.

It is an amenable number.

20871689 is a deficient number, since it is larger than the sum of its proper divisors (1).

20871689 is an equidigital number, since it uses as much as digits as its factorization.

20871689 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48384, while the sum is 41.

The square root of 20871689 is about 4568.5543665365. The cubic root of 20871689 is about 275.3293640450.

The spelling of 20871689 in words is "twenty million, eight hundred seventy-one thousand, six hundred eighty-nine".