1821861820 has 24 divisors (see below), whose sum is σ = 3828778128. Its totient is φ = 728198400.

The previous prime is 1821861817. The next prime is 1821861827. The reversal of 1821861820 is 281681281.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 1821861820.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1821861827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6246 + ... + 60685.

It is an arithmetic number, because the mean of its divisors is an integer number (159532422).

Almost surely, 2^1821861820 is an apocalyptic number.

1821861820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1821861820 is an abundant number, since it is smaller than the sum of its proper divisors (2006916308).

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

1821861820 is a wasteful number, since it uses less digits than its factorization.

1821861820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 68301 (or 68299 counting only the distinct ones).

The product of its (nonzero) digits is 12288, while the sum is 37.

The square root of 1821861820 is about 42683.2733046565. The cubic root of 1821861820 is about 1221.3453357582.

The spelling of 1821861820 in words is "one billion, eight hundred twenty-one million, eight hundred sixty-one thousand, eight hundred twenty".