19802009 has 4 divisors (see below), whose sum is σ = 20844240. Its totient is φ = 18759780.

The previous prime is 19801997. The next prime is 19802017. The reversal of 19802009 is 90020891.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 90020891 = 401 ⋅224491.

It is a cyclic number.

It is not a de Polignac number, because 19802009 - 2²⁰ = 18753433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19802089) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 521087 + ... + 521124.

It is an arithmetic number, because the mean of its divisors is an integer number (5211060).

Almost surely, 2^19802009 is an apocalyptic number.

19802009 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

It is an amenable number.

19802009 is a deficient number, since it is larger than the sum of its proper divisors (1042231).

19802009 is a wasteful number, since it uses less digits than its factorization.

19802009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1042230.

The product of its (nonzero) digits is 1296, while the sum is 29.

The square root of 19802009 is about 4449.9448311187. The cubic root of 19802009 is about 270.5430724664.

The spelling of 19802009 in words is "nineteen million, eight hundred two thousand, nine".