20218609 has 2 divisors, whose sum is σ = 20218610. Its totient is φ = 20218608.

The previous prime is 20218607. The next prime is 20218619. The reversal of 20218609 is 90681202.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17977600 + 2241009 = 4240^2 + 1497^2 .

It is a cyclic number.

It is not a de Polignac number, because 20218609 - 2¹ = 20218607 is a prime.

Together with 20218607, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (20218607) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10109304 + 10109305.

It is an arithmetic number, because the mean of its divisors is an integer number (10109305).

Almost surely, 2^20218609 is an apocalyptic number.

It is an amenable number.

20218609 is a deficient number, since it is larger than the sum of its proper divisors (1).

20218609 is an equidigital number, since it uses as much as digits as its factorization.

20218609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 20218609 is about 4496.5107583547. The cubic root of 20218609 is about 272.4271735359.

The spelling of 20218609 in words is "twenty million, two hundred eighteen thousand, six hundred nine".