1809666421 has 2 divisors, whose sum is σ = 1809666422. Its totient is φ = 1809666420.

The previous prime is 1809666407. The next prime is 1809666479. The reversal of 1809666421 is 1246669081.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1055340196 + 754326225 = 32486^2 + 27465^2 .

It is a cyclic number.

It is not a de Polignac number, because 1809666421 - 2⁷ = 1809666293 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1809666401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 904833210 + 904833211.

It is an arithmetic number, because the mean of its divisors is an integer number (904833211).

Almost surely, 2^1809666421 is an apocalyptic number.

It is an amenable number.

1809666421 is a deficient number, since it is larger than the sum of its proper divisors (1).

1809666421 is an equidigital number, since it uses as much as digits as its factorization.

1809666421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 124416, while the sum is 43.

The square root of 1809666421 is about 42540.1742003956. The cubic root of 1809666421 is about 1218.6140359181.

The spelling of 1809666421 in words is "one billion, eight hundred nine million, six hundred sixty-six thousand, four hundred twenty-one".