19999709 has 4 divisors (see below), whose sum is σ = 20377116.
Its totient is φ = 19622304.
The previous prime is 19999697. The next prime is 19999729. The reversal of 19999709 is 90799991.
It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90799991 = 389 ⋅233419.
It can be written as a sum of positive squares in 2 ways, for example, as 17455684 + 2544025 = 4178^2 + 1595^2
It is a cyclic number.
It is not a de Polignac number, because 19999709 - 220 = 18951133 is a prime.
It is a Harshad number since it is a multiple of its sum of digits (53), and also a Moran number because the ratio is a prime number: 377353 = 19999709 / (1 + 9 + 9 + 9 + 9 + 7 + 0 + 9).
It is a Duffinian number.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (19999729) 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, 188624 + ... + 188729.
It is an arithmetic number, because the mean of its divisors is an integer number (5094279).
Almost surely, 219999709 is an apocalyptic number.
It is an amenable number.
19999709 is a deficient number, since it is larger than the sum of its proper divisors (377407).
19999709 is an equidigital number, since it uses as much as digits as its factorization.
19999709 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 377406.
The product of its (nonzero) digits is 413343, while the sum is 53.
The square root of 19999709 is about 4472.1034200922.
The cubic root of 19999709 is about 271.4404451606.
The spelling of 19999709 in words is "nineteen million, nine hundred ninety-nine thousand, seven hundred nine".