809121920 has 128 divisors (see below), whose sum is σ = 2031644160. Its totient is φ = 307777536.

The previous prime is 809121913. The next prime is 809121941. The reversal of 809121920 is 29121908.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (128).

It is a Harshad number since it is a multiple of its sum of digits (32).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1112597 + ... + 1113323.

It is an arithmetic number, because the mean of its divisors is an integer number (15872220).

Almost surely, 2^809121920 is an apocalyptic number.

809121920 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 809121920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1015822080).

809121920 is an abundant number, since it is smaller than the sum of its proper divisors (1222522240).

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

809121920 is a wasteful number, since it uses less digits than its factorization.

809121920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 830 (or 818 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 32.

The square root of 809121920 is about 28445.0684653773. The cubic root of 809121920 is about 931.8327906480.

The spelling of 809121920 in words is "eight hundred nine million, one hundred twenty-one thousand, nine hundred twenty".