1921109209 has 4 divisors (see below), whose sum is σ = 2022220240. Its totient is φ = 1819998180.

The previous prime is 1921109189. The next prime is 1921109219. The reversal of 1921109209 is 9029011291.

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.

It is a cyclic number.

It is not a de Polignac number, because 1921109209 - 2⁷ = 1921109081 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1921109219) 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, 50555487 + ... + 50555524.

It is an arithmetic number, because the mean of its divisors is an integer number (505555060).

Almost surely, 2^1921109209 is an apocalyptic number.

1921109209 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

It is an amenable number.

1921109209 is a deficient number, since it is larger than the sum of its proper divisors (101111031).

1921109209 is a wasteful number, since it uses less digits than its factorization.

1921109209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 101111030.

The product of its (nonzero) digits is 2916, while the sum is 34.

The square root of 1921109209 is about 43830.4598310353. The cubic root of 1921109209 is about 1243.1323014624.

The spelling of 1921109209 in words is "one billion, nine hundred twenty-one million, one hundred nine thousand, two hundred nine".