1821721920 has 56 divisors (see below), whose sum is σ = 5783970144. Its totient is φ = 485792256.

The previous prime is 1821721897. The next prime is 1821721939. The reversal of 1821721920 is 291271281.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 947854 + ... + 949773.

Almost surely, 2^1821721920 is an apocalyptic number.

1821721920 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1821721920 is an abundant number, since it is smaller than the sum of its proper divisors (3962248224).

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

1821721920 is a wasteful number, since it uses less digits than its factorization.

1821721920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1897647 (or 1897637 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 33.

The square root of 1821721920 is about 42681.6344579258. The cubic root of 1821721920 is about 1221.3140727604.

The spelling of 1821721920 in words is "one billion, eight hundred twenty-one million, seven hundred twenty-one thousand, nine hundred twenty".