20181820 has 48 divisors (see below), whose sum is σ = 43662528. Its totient is φ = 7833600.

The previous prime is 20181809. The next prime is 20181823. The reversal of 20181820 is 2818102.

It is a junction number, because it is equal to n+sod(n) for n = 20181791 and 20181800.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20181823) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 195889 + ... + 195991.

It is an arithmetic number, because the mean of its divisors is an integer number (909636).

Almost surely, 2^20181820 is an apocalyptic number.

20181820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20181820 is an abundant number, since it is smaller than the sum of its proper divisors (23480708).

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

20181820 is a wasteful number, since it uses less digits than its factorization.

20181820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 310 (or 308 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 22.

The square root of 20181820 is about 4492.4180571269. The cubic root of 20181820 is about 272.2618405633.

Adding to 20181820 its reverse (2818102), we get a palindrome (22999922).

The spelling of 20181820 in words is "twenty million, one hundred eighty-one thousand, eight hundred twenty".