1638840 has 64 divisors (see below), whose sum is σ = 5621760. Its totient is φ = 374400.

The previous prime is 1638821. The next prime is 1638869. The reversal of 1638840 is 488361.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 1638798 and 1638807.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 136 + ... + 1815.

It is an arithmetic number, because the mean of its divisors is an integer number (87840).

2^1638840 is an apocalyptic number.

1638840 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1638840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2810880).

1638840 is an abundant number, since it is smaller than the sum of its proper divisors (3982920).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1638840 is a wasteful number, since it uses less digits than its factorization.

1638840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1972 (or 1968 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 30.

The square root of 1638840 is about 1280.1718634621. The cubic root of 1638840 is about 117.8995602272.

The spelling of 1638840 in words is "one million, six hundred thirty-eight thousand, eight hundred forty".