1821801816 has 24 divisors (see below), whose sum is σ = 4934046780. Its totient is φ = 607267248.

The previous prime is 1821801809. The next prime is 1821801841. The reversal of 1821801816 is 6181081281.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (24).

It is a Harshad number since it is a multiple of its sum of digits (36).

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 5 ways as a sum of consecutive naturals, for example, 12651330 + ... + 12651473.

Almost surely, 2^1821801816 is an apocalyptic number.

It is an amenable number.

1821801816 is an abundant number, since it is smaller than the sum of its proper divisors (3112244964).

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

1821801816 is a wasteful number, since it uses less digits than its factorization.

1821801816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25302815 (or 25302808 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 36.

The square root of 1821801816 is about 42682.5704005745. The cubic root of 1821801816 is about 1221.3319270556.

The spelling of 1821801816 in words is "one billion, eight hundred twenty-one million, eight hundred one thousand, eight hundred sixteen".