1998421 has 6 divisors (see below), whose sum is σ = 2042466. Its totient is φ = 1954800.

The previous prime is 1998413. The next prime is 1998427. The reversal of 1998421 is 1248991.

It can be written as a sum of positive squares in 3 ways, for example, as 617796 + 1380625 = 786^2 + 1175^2 .

It is not a de Polignac number, because 1998421 - 2³ = 1998413 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1998427) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 10951 + ... + 11131.

It is an arithmetic number, because the mean of its divisors is an integer number (340411).

2^1998421 is an apocalyptic number.

It is an amenable number.

1998421 is a deficient number, since it is larger than the sum of its proper divisors (44045).

1998421 is an frugal number, since it uses more digits than its factorization.

1998421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 423 (or 242 counting only the distinct ones).

The product of its digits is 5184, while the sum is 34.

The square root of 1998421 is about 1413.6551913391. The cubic root of 1998421 is about 125.9589393376.

The spelling of 1998421 in words is "one million, nine hundred ninety-eight thousand, four hundred twenty-one".