1809799821 has 16 divisors (see below), whose sum is σ = 2838902400. Its totient is φ = 1135560384.

The previous prime is 1809799801. The next prime is 1809799829. The reversal of 1809799821 is 1289979081.

It is not a de Polignac number, because 1809799821 - 2⁹ = 1809799309 is a prime.

It is a Smith number, since the sum of its digits (54) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1809799829) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1971001 + ... + 1971918.

It is an arithmetic number, because the mean of its divisors is an integer number (177431400).

Almost surely, 2^1809799821 is an apocalyptic number.

It is an amenable number.

1809799821 is a deficient number, since it is larger than the sum of its proper divisors (1029102579).

1809799821 is a wasteful number, since it uses less digits than its factorization.

1809799821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3942945 (or 3942939 counting only the distinct ones).

The product of its (nonzero) digits is 653184, while the sum is 54.

The square root of 1809799821 is about 42541.7421011411. The cubic root of 1809799821 is about 1218.6439786589.

The spelling of 1809799821 in words is "one billion, eight hundred nine million, seven hundred ninety-nine thousand, eight hundred twenty-one".