20908649 has 2 divisors, whose sum is σ = 20908650. Its totient is φ = 20908648.

The previous prime is 20908639. The next prime is 20908651. The reversal of 20908649 is 94680902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20866624 + 42025 = 4568^2 + 205^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20908649 is a prime.

It is a Sophie Germain prime.

Together with 20908651, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (20908609) 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, 10454324 + 10454325.

It is an arithmetic number, because the mean of its divisors is an integer number (10454325).

Almost surely, 2^20908649 is an apocalyptic number.

It is an amenable number.

20908649 is a deficient number, since it is larger than the sum of its proper divisors (1).

20908649 is an equidigital number, since it uses as much as digits as its factorization.

20908649 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 31104, while the sum is 38.

The square root of 20908649 is about 4572.5976206091. The cubic root of 20908649 is about 275.4917877708.

The spelling of 20908649 in words is "twenty million, nine hundred eight thousand, six hundred forty-nine".