20009999 has 2 divisors, whose sum is σ = 20010000. Its totient is φ = 20009998.

The previous prime is 20009987. The next prime is 20010017. The reversal of 20009999 is 99990002.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20009999 - 2¹² = 20005903 is a prime.

20009999 is a modest number, since divided by 9999 gives 2000 as remainder.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20009929) 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, 10004999 + 10005000.

It is an arithmetic number, because the mean of its divisors is an integer number (10005000).

Almost surely, 2^20009999 is an apocalyptic number.

20009999 is a deficient number, since it is larger than the sum of its proper divisors (1).

20009999 is an equidigital number, since it uses as much as digits as its factorization.

20009999 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13122, while the sum is 38.

The square root of 20009999 is about 4473.2537374935. The cubic root of 20009999 is about 271.4869898926.

It can be divided in two parts, 20009 and 999, that multiplied together give a palindrome (19988991).

The spelling of 20009999 in words is "twenty million, nine thousand, nine hundred ninety-nine".