19998739 has 4 divisors (see below), whose sum is σ = 20023920. Its totient is φ = 19973560.

The previous prime is 19998733. The next prime is 19998743. The reversal of 19998739 is 93789991.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 19998739 - 2¹⁹ = 19474451 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 19998739.

It is not an unprimeable number, because it can be changed into a prime (19998733) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11359 + ... + 13000.

It is an arithmetic number, because the mean of its divisors is an integer number (5005980).

Almost surely, 2^19998739 is an apocalyptic number.

19998739 is a deficient number, since it is larger than the sum of its proper divisors (25181).

19998739 is an equidigital number, since it uses as much as digits as its factorization.

19998739 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25180.

The product of its digits is 1102248, while the sum is 55.

The square root of 19998739 is about 4471.9949686913. The cubic root of 19998739 is about 271.4360567386.

The spelling of 19998739 in words is "nineteen million, nine hundred ninety-eight thousand, seven hundred thirty-nine".