1821409920 has 768 divisors, whose sum is σ = 7733232000. Its totient is φ = 389283840.

The previous prime is 1821409907. The next prime is 1821409921. The reversal of 1821409920 is 299041281.

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

It is not an unprimeable number, because it can be changed into a prime (1821409921) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 20465236 + ... + 20465324.

Almost surely, 2^1821409920 is an apocalyptic number.

1821409920 is a gapful number since it is divisible by the number (10) 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 1821409920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3866616000).

1821409920 is an abundant number, since it is smaller than the sum of its proper divisors (5911822080).

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

1821409920 is a wasteful number, since it uses less digits than its factorization.

1821409920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 161 (or 146 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 36.

The square root of 1821409920 is about 42677.9793336095. The cubic root of 1821409920 is about 1221.2443453700.

The spelling of 1821409920 in words is "one billion, eight hundred twenty-one million, four hundred nine thousand, nine hundred twenty".