1678421 has 2 divisors, whose sum is σ = 1678422. Its totient is φ = 1678420.

The previous prime is 1678409. The next prime is 1678423. The reversal of 1678421 is 1248761.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1661521 + 16900 = 1289^2 + 130^2 .

It is a cyclic number.

It is not a de Polignac number, because 1678421 - 2¹⁸ = 1416277 is a prime.

Together with 1678423, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1678423) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 839210 + 839211.

It is an arithmetic number, because the mean of its divisors is an integer number (839211).

2^1678421 is an apocalyptic number.

It is an amenable number.

1678421 is a deficient number, since it is larger than the sum of its proper divisors (1).

1678421 is an equidigital number, since it uses as much as digits as its factorization.

1678421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2688, while the sum is 29.

The square root of 1678421 is about 1295.5388840170. The cubic root of 1678421 is about 118.8411835207.

The spelling of 1678421 in words is "one million, six hundred seventy-eight thousand, four hundred twenty-one".