1978421 has 2 divisors, whose sum is σ = 1978422. Its totient is φ = 1978420.

The previous prime is 1978411. The next prime is 1978423. The reversal of 1978421 is 1248791.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1188100 + 790321 = 1090^2 + 889^2 .

It is a cyclic number.

It is not a de Polignac number, because 1978421 - 2¹⁸ = 1716277 is a prime.

Together with 1978423, 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 (1978423) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 989210 + 989211.

It is an arithmetic number, because the mean of its divisors is an integer number (989211).

2^1978421 is an apocalyptic number.

It is an amenable number.

1978421 is a deficient number, since it is larger than the sum of its proper divisors (1).

1978421 is an equidigital number, since it uses as much as digits as its factorization.

1978421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4032, while the sum is 32.

The square root of 1978421 is about 1406.5635428234. The cubic root of 1978421 is about 125.5373348602.

The spelling of 1978421 in words is "one million, nine hundred seventy-eight thousand, four hundred twenty-one".