1921009 has 4 divisors (see below), whose sum is σ = 1926720. Its totient is φ = 1915300.

The previous prime is 1920991. The next prime is 1921013. The reversal of 1921009 is 9001291.

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: 9001291 = 13 ⋅692407.

It is a cyclic number.

It is not a de Polignac number, because 1921009 - 2⁹ = 1920497 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1921069) 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, 2317 + ... + 3034.

It is an arithmetic number, because the mean of its divisors is an integer number (481680).

2^1921009 is an apocalyptic number.

It is an amenable number.

1921009 is a deficient number, since it is larger than the sum of its proper divisors (5711).

1921009 is an equidigital number, since it uses as much as digits as its factorization.

1921009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5710.

The product of its (nonzero) digits is 162, while the sum is 22.

The square root of 1921009 is about 1386.0046897468. The cubic root of 1921009 is about 124.3110686309.

It can be divided in two parts, 19 and 21009, that multiplied together give a triangular number (399171 = T₈₉₃).

The spelling of 1921009 in words is "one million, nine hundred twenty-one thousand, nine".