1801819820 has 24 divisors (see below), whose sum is σ = 3905881728. Its totient is φ = 697478400.

The previous prime is 1801819819. The next prime is 1801819823. The reversal of 1801819820 is 289181081.

It is a happy number.

It is a Smith number, since the sum of its digits (38) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (1801819823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1452461 + ... + 1453700.

It is an arithmetic number, because the mean of its divisors is an integer number (162745072).

Almost surely, 2^1801819820 is an apocalyptic number.

1801819820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1801819820 is an abundant number, since it is smaller than the sum of its proper divisors (2104061908).

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

1801819820 is a wasteful number, since it uses less digits than its factorization.

1801819820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2906201 (or 2906199 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 38.

The square root of 1801819820 is about 42447.8482375727. The cubic root of 1801819820 is about 1216.8502059591.

The spelling of 1801819820 in words is "one billion, eight hundred one million, eight hundred nineteen thousand, eight hundred twenty".