821996400 has 120 divisors (see below), whose sum is σ = 2639674800. Its totient is φ = 218654720.

The previous prime is 821996389. The next prime is 821996407. The reversal of 821996400 is 4699128.

It is a tau number, because it is divible by the number of its divisors (120).

It is a super-2 number, since 2×821996400² = 1351356163225920000, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821996407) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 783076 + ... + 784124.

It is an arithmetic number, because the mean of its divisors is an integer number (21997290).

Almost surely, 2^821996400 is an apocalyptic number.

821996400 is a gapful number since it is divisible by the number (80) 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 821996400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1319837400).

821996400 is an abundant number, since it is smaller than the sum of its proper divisors (1817678400).

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

821996400 is a wasteful number, since it uses less digits than its factorization.

821996400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1723 (or 1712 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 39.

The square root of 821996400 is about 28670.4795913846. The cubic root of 821996400 is about 936.7491445689.

The spelling of 821996400 in words is "eight hundred twenty-one million, nine hundred ninety-six thousand, four hundred".