20989609 has 2 divisors, whose sum is σ = 20989610. Its totient is φ = 20989608.

The previous prime is 20989607. The next prime is 20989613. The reversal of 20989609 is 90698902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11971600 + 9018009 = 3460^2 + 3003^2 .

It is a cyclic number.

It is not a de Polignac number, because 20989609 - 2¹ = 20989607 is a prime.

Together with 20989607, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (20989601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10494804 + 10494805.

It is an arithmetic number, because the mean of its divisors is an integer number (10494805).

Almost surely, 2^20989609 is an apocalyptic number.

It is an amenable number.

20989609 is a deficient number, since it is larger than the sum of its proper divisors (1).

20989609 is an equidigital number, since it uses as much as digits as its factorization.

20989609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 69984, while the sum is 43.

The square root of 20989609 is about 4581.4418036247. The cubic root of 20989609 is about 275.8469053987.

The spelling of 20989609 in words is "twenty million, nine hundred eighty-nine thousand, six hundred nine".