1721920 has 28 divisors (see below), whose sum is σ = 4101084. Its totient is φ = 688640.

The previous prime is 1721911. The next prime is 1721921. The reversal of 1721920 is 291271.

It can be written as a sum of positive squares in 2 ways, for example, as 589824 + 1132096 = 768^2 + 1064^2 .

It is a nialpdrome in base 8.

It is a junction number, because it is equal to n+sod(n) for n = 1721891 and 1721900.

It is not an unprimeable number, because it can be changed into a prime (1721921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2371 + ... + 3010.

2^1721920 is an apocalyptic number.

1721920 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1721920 is an abundant number, since it is smaller than the sum of its proper divisors (2379164).

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

1721920 is an equidigital number, since it uses as much as digits as its factorization.

1721920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5398 (or 5388 counting only the distinct ones).

The product of its (nonzero) digits is 252, while the sum is 22.

The square root of 1721920 is about 1312.2194938348. The cubic root of 1721920 is about 119.8590938695.

The spelling of 1721920 in words is "one million, seven hundred twenty-one thousand, nine hundred twenty".