20105840 has 20 divisors (see below), whose sum is σ = 46746264. Its totient is φ = 8042304.

The previous prime is 20105807. The next prime is 20105861. The reversal of 20105840 is 4850102.

It is a tau number, because it is divible by the number of its divisors (20).

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 125582 + ... + 125741.

Almost surely, 2^20105840 is an apocalyptic number.

20105840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20105840 is an abundant number, since it is smaller than the sum of its proper divisors (26640424).

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

20105840 is a wasteful number, since it uses less digits than its factorization.

20105840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 251336 (or 251330 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 20.

The square root of 20105840 is about 4483.9536126057. The cubic root of 20105840 is about 271.9197427573.

Adding to 20105840 its reverse (4850102), we get a palindrome (24955942).

The spelling of 20105840 in words is "twenty million, one hundred five thousand, eight hundred forty".