1921789 has 2 divisors, whose sum is σ = 1921790. Its totient is φ = 1921788.

The previous prime is 1921781. The next prime is 1921813. The reversal of 1921789 is 9871291.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1863225 + 58564 = 1365^2 + 242^2 .

It is an emirp because it is prime and its reverse (9871291) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1921789 - 2³ = 1921781 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1921781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 960894 + 960895.

It is an arithmetic number, because the mean of its divisors is an integer number (960895).

2^1921789 is an apocalyptic number.

It is an amenable number.

1921789 is a deficient number, since it is larger than the sum of its proper divisors (1).

1921789 is an equidigital number, since it uses as much as digits as its factorization.

1921789 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 37.

The square root of 1921789 is about 1386.2860455187. The cubic root of 1921789 is about 124.3278913029.

It can be divided in two parts, 19217 and 89, that added together give a triangular number (19306 = T₁₉₆).

The spelling of 1921789 in words is "one million, nine hundred twenty-one thousand, seven hundred eighty-nine".