3978421 has 2 divisors, whose sum is σ = 3978422. Its totient is φ = 3978420.

The previous prime is 3978349. The next prime is 3978431. The reversal of 3978421 is 1248793.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 3944196 + 34225 = 1986^2 + 185^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-3978421 is a prime.

3978421 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (3978431) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1989210 + 1989211.

It is an arithmetic number, because the mean of its divisors is an integer number (1989211).

Almost surely, 2^3978421 is an apocalyptic number.

It is an amenable number.

3978421 is a deficient number, since it is larger than the sum of its proper divisors (1).

3978421 is an equidigital number, since it uses as much as digits as its factorization.

3978421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12096, while the sum is 34.

The square root of 3978421 is about 1994.5979544760. The cubic root of 3978421 is about 158.4541359403.

The spelling of 3978421 in words is "three million, nine hundred seventy-eight thousand, four hundred twenty-one".