19805999 has 8 divisors (see below), whose sum is σ = 21056880. Its totient is φ = 18576000.

The previous prime is 19805987. The next prime is 19806001. The reversal of 19805999 is 99950891.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 19805999 - 2⁴ = 19805983 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19805909) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3242 + ... + 7079.

It is an arithmetic number, because the mean of its divisors is an integer number (2632110).

Almost surely, 2^19805999 is an apocalyptic number.

19805999 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

19805999 is a deficient number, since it is larger than the sum of its proper divisors (1250881).

19805999 is a wasteful number, since it uses less digits than its factorization.

19805999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10441.

The product of its (nonzero) digits is 262440, while the sum is 50.

The square root of 19805999 is about 4450.3931287022. The cubic root of 19805999 is about 270.5612422451.

It can be divided in two parts, 19805 and 999, that multiplied together give a triangular number (19785195 = T₆₂₉₀).

The spelling of 19805999 in words is "nineteen million, eight hundred five thousand, nine hundred ninety-nine".