1638009 has 32 divisors (see below), whose sum is σ = 2662400. Its totient is φ = 991440.

The previous prime is 1637983. The next prime is 1638011. The reversal of 1638009 is 9008361.

It is not a de Polignac number, because 1638009 - 2⁹ = 1637497 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1638019) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 15852 + ... + 15954.

It is an arithmetic number, because the mean of its divisors is an integer number (83200).

2^1638009 is an apocalyptic number.

1638009 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

It is an amenable number.

1638009 is a deficient number, since it is larger than the sum of its proper divisors (1024391).

1638009 is a wasteful number, since it uses less digits than its factorization.

1638009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 162 (or 156 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 27.

The square root of 1638009 is about 1279.8472565115. The cubic root of 1638009 is about 117.8796292396.

It can be divided in two parts, 16 and 38009, that added together give a square (38025 = 195²).

The spelling of 1638009 in words is "one million, six hundred thirty-eight thousand, nine".