1821998556 has 72 divisors (see below), whose sum is σ = 5494932240. Its totient is φ = 520569504.

The previous prime is 1821998539. The next prime is 1821998593. The reversal of 1821998556 is 6558991281.

1821998556 is a `hidden beast` number, since 1 + 82 + 1 + 9 + 9 + 8 + 556 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 166855 + ... + 177438.

Almost surely, 2^1821998556 is an apocalyptic number.

It is an amenable number.

1821998556 is an abundant number, since it is smaller than the sum of its proper divisors (3672933684).

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

1821998556 is a wasteful number, since it uses less digits than its factorization.

1821998556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 344320 (or 344305 counting only the distinct ones).

The product of its digits is 1555200, while the sum is 54.

The square root of 1821998556 is about 42684.8750261729. The cubic root of 1821998556 is about 1221.3758901607.

The spelling of 1821998556 in words is "one billion, eight hundred twenty-one million, nine hundred ninety-eight thousand, five hundred fifty-six".