20399999 has 4 divisors (see below), whose sum is σ = 20409840. Its totient is φ = 20390160.

The previous prime is 20399993. The next prime is 20400013. The reversal of 20399999 is 99999302.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 20399999 - 2²⁴ = 3622783 is a prime.

It is a Duffinian number.

20399999 is a modest number, since divided by 9999 gives 2039 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20399993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 467 + ... + 6404.

It is an arithmetic number, because the mean of its divisors is an integer number (5102460).

Almost surely, 2^20399999 is an apocalyptic number.

20399999 is a deficient number, since it is larger than the sum of its proper divisors (9841).

20399999 is an equidigital number, since it uses as much as digits as its factorization.

20399999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9840.

The product of its (nonzero) digits is 354294, while the sum is 50.

The square root of 20399999 is about 4516.6358055526. The cubic root of 20399999 is about 273.2394371448.

The spelling of 20399999 in words is "twenty million, three hundred ninety-nine thousand, nine hundred ninety-nine".