20984609 has 2 divisors, whose sum is σ = 20984610. Its totient is φ = 20984608.

The previous prime is 20984599. The next prime is 20984611. The reversal of 20984609 is 90648902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10923025 + 10061584 = 3305^2 + 3172^2 .

It is a cyclic number.

It is not a de Polignac number, because 20984609 - 2¹² = 20980513 is a prime.

Together with 20984611, 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 (20984629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10492304 + 10492305.

It is an arithmetic number, because the mean of its divisors is an integer number (10492305).

Almost surely, 2^20984609 is an apocalyptic number.

It is an amenable number.

20984609 is a deficient number, since it is larger than the sum of its proper divisors (1).

20984609 is an equidigital number, since it uses as much as digits as its factorization.

20984609 is an evil number, because the sum of its binary digits is even.

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

The square root of 20984609 is about 4580.8960913778. The cubic root of 20984609 is about 275.8250002097.

The spelling of 20984609 in words is "twenty million, nine hundred eighty-four thousand, six hundred nine".