1638421 has 4 divisors (see below), whose sum is σ = 1654432. Its totient is φ = 1622412.

The previous prime is 1638353. The next prime is 1638431. The reversal of 1638421 is 1248361.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1248361 = 17 ⋅73433.

It is a cyclic number.

It is not a de Polignac number, because 1638421 - 2¹¹ = 1636373 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 (1638431) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7851 + ... + 8056.

It is an arithmetic number, because the mean of its divisors is an integer number (413608).

2^1638421 is an apocalyptic number.

It is an amenable number.

1638421 is a deficient number, since it is larger than the sum of its proper divisors (16011).

1638421 is a wasteful number, since it uses less digits than its factorization.

1638421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16010.

The product of its digits is 1152, while the sum is 25.

The square root of 1638421 is about 1280.0082030987. The cubic root of 1638421 is about 117.8895116305.

The spelling of 1638421 in words is "one million, six hundred thirty-eight thousand, four hundred twenty-one".