20931289 has 2 divisors, whose sum is σ = 20931290. Its totient is φ = 20931288.

The previous prime is 20931263. The next prime is 20931347. The reversal of 20931289 is 98213902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15936064 + 4995225 = 3992^2 + 2235^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20931289 is a prime.

It is not a weakly prime, because it can be changed into another prime (20931259) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10465644 + 10465645.

It is an arithmetic number, because the mean of its divisors is an integer number (10465645).

Almost surely, 2^20931289 is an apocalyptic number.

It is an amenable number.

20931289 is a deficient number, since it is larger than the sum of its proper divisors (1).

20931289 is an equidigital number, since it uses as much as digits as its factorization.

20931289 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7776, while the sum is 34.

The square root of 20931289 is about 4575.0725677305. The cubic root of 20931289 is about 275.5911865767.

The spelling of 20931289 in words is "twenty million, nine hundred thirty-one thousand, two hundred eighty-nine".