1638399 has 16 divisors (see below), whose sum is σ = 2539520. Its totient is φ = 920160.

The previous prime is 1638353. The next prime is 1638431. The reversal of 1638399 is 9938361.

It is a Cunningham number, because it is equal to 1280²-1.

It is not a de Polignac number, because 1638399 - 2⁹ = 1637887 is a prime.

It is a Duffinian number.

1638399 is a lucky number.

It is a plaindrome in base 16.

It is a zygodrome in base 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1638349) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 642 + ... + 1920.

It is an arithmetic number, because the mean of its divisors is an integer number (158720).

2^1638399 is an apocalyptic number.

1638399 is a deficient number, since it is larger than the sum of its proper divisors (901121).

1638399 is a wasteful number, since it uses less digits than its factorization.

1638399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1350.

The product of its digits is 34992, while the sum is 39.

The square root of 1638399 is about 1279.9996093749. Note that the first 3 decimals coincide. The cubic root of 1638399 is about 117.8889839719. Note that the first 3 decimals are identical.

The spelling of 1638399 in words is "one million, six hundred thirty-eight thousand, three hundred ninety-nine".