20663989 has 2 divisors, whose sum is σ = 20663990. Its totient is φ = 20663988.

The previous prime is 20663987. The next prime is 20664013. The reversal of 20663989 is 98936602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20629764 + 34225 = 4542^2 + 185^2 .

It is a cyclic number.

It is not a de Polignac number, because 20663989 - 2¹ = 20663987 is a prime.

Together with 20663987, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20663987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10331994 + 10331995.

It is an arithmetic number, because the mean of its divisors is an integer number (10331995).

Almost surely, 2^20663989 is an apocalyptic number.

It is an amenable number.

20663989 is a deficient number, since it is larger than the sum of its proper divisors (1).

20663989 is an equidigital number, since it uses as much as digits as its factorization.

20663989 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 139968, while the sum is 43.

The square root of 20663989 is about 4545.7660520533. The cubic root of 20663989 is about 274.4130246023.

The spelling of 20663989 in words is "twenty million, six hundred sixty-three thousand, nine hundred eighty-nine".