1809990 has 144 divisors (see below), whose sum is σ = 6166368. Its totient is φ = 359424.

The previous prime is 1809979. The next prime is 1809991. The reversal of 1809990 is 999081.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1809991) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 106462 + ... + 106478.

It is an arithmetic number, because the mean of its divisors is an integer number (42822).

2^1809990 is an apocalyptic number.

1809990 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 1809990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3083184).

1809990 is an abundant number, since it is smaller than the sum of its proper divisors (4356378).

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

1809990 is a wasteful number, since it uses less digits than its factorization.

1809990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63 (or 47 counting only the distinct ones).

The product of its (nonzero) digits is 5832, while the sum is 36.

The square root of 1809990 is about 1345.3586882315. The cubic root of 1809990 is about 121.8686663375.

The spelling of 1809990 in words is "one million, eight hundred nine thousand, nine hundred ninety".