821197440 has 640 divisors, whose sum is σ = 3507102720. Its totient is φ = 179159040.

The previous prime is 821197439. The next prime is 821197463. The reversal of 821197440 is 44791128.

821197440 is a `hidden beast` number, since 8 + 21 + 197 + 440 = 666.

It is a tau number, because it is divible by the number of its divisors (640).

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

It is a junction number, because it is equal to n+sod(n) for n = 821197395 and 821197404.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 11249244 + ... + 11249316.

It is an arithmetic number, because the mean of its divisors is an integer number (5479848).

Almost surely, 2^821197440 is an apocalyptic number.

821197440 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 821197440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1753551360).

821197440 is an abundant number, since it is smaller than the sum of its proper divisors (2685905280).

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

821197440 is a wasteful number, since it uses less digits than its factorization.

821197440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 142 (or 121 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 36.

The square root of 821197440 is about 28656.5427084287. The cubic root of 821197440 is about 936.4455472493.

The spelling of 821197440 in words is "eight hundred twenty-one million, one hundred ninety-seven thousand, four hundred forty".