19981806 has 64 divisors (see below), whose sum is σ = 46099200. Its totient is φ = 5723136.

The previous prime is 19981777. The next prime is 19981807. The reversal of 19981806 is 60818991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19981807) 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, 143685 + ... + 143823.

It is an arithmetic number, because the mean of its divisors is an integer number (720300).

Almost surely, 2^19981806 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 19981806, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23049600).

19981806 is an abundant number, since it is smaller than the sum of its proper divisors (26117394).

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

19981806 is a wasteful number, since it uses less digits than its factorization.

19981806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 273.

The product of its (nonzero) digits is 31104, while the sum is 42.

The square root of 19981806 is about 4470.1013411331. The cubic root of 19981806 is about 271.3594264975.

The spelling of 19981806 in words is "nineteen million, nine hundred eighty-one thousand, eight hundred six".