1817981820 has 240 divisors, whose sum is σ = 5921790336. Its totient is φ = 466560000.

The previous prime is 1817981777. The next prime is 1817981831. The reversal of 1817981820 is 281897181.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

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 79 ways as a sum of consecutive naturals, for example, 6708285 + ... + 6708555.

Almost surely, 2^1817981820 is an apocalyptic number.

1817981820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1817981820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2960895168).

1817981820 is an abundant number, since it is smaller than the sum of its proper divisors (4103808516).

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

1817981820 is a wasteful number, since it uses less digits than its factorization.

1817981820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 434 (or 423 counting only the distinct ones).

The product of its (nonzero) digits is 64512, while the sum is 45.

The square root of 1817981820 is about 42637.7980200667. The cubic root of 1817981820 is about 1220.4776907465.

It can be divided in two parts, 18179 and 81820, that added together give a palindrome (99999).

The spelling of 1817981820 in words is "one billion, eight hundred seventeen million, nine hundred eighty-one thousand, eight hundred twenty".