821811900 has 144 divisors (see below), whose sum is σ = 2926590464. Its totient is φ = 173387520.

The previous prime is 821811871. The next prime is 821811911. The reversal of 821811900 is 9118128.

It is a super-2 number, since 2×821811900² = 1350749597963220000, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

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 47 ways as a sum of consecutive naturals, for example, 12249 + ... + 42351.

Almost surely, 2^821811900 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 821811900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1463295232).

821811900 is an abundant number, since it is smaller than the sum of its proper divisors (2104778564).

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

821811900 is a wasteful number, since it uses less digits than its factorization.

821811900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30140 (or 30133 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 30.

The square root of 821811900 is about 28667.2618155275. The cubic root of 821811900 is about 936.6790537714.

The spelling of 821811900 in words is "eight hundred twenty-one million, eight hundred eleven thousand, nine hundred".