821191680 has 264 divisors, whose sum is σ = 2896979904. Its totient is φ = 215040000.

The previous prime is 821191663. The next prime is 821191739. The reversal of 821191680 is 86191128.

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 polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3271555 + ... + 3271805.

Almost surely, 2^821191680 is an apocalyptic number.

821191680 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 821191680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1448489952).

821191680 is an abundant number, since it is smaller than the sum of its proper divisors (2075788224).

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

821191680 is a wasteful number, since it uses less digits than its factorization.

821191680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 353 (or 332 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 36.

The square root of 821191680 is about 28656.4422076433. The cubic root of 821191680 is about 936.4433577885.

The spelling of 821191680 in words is "eight hundred twenty-one million, one hundred ninety-one thousand, six hundred eighty".