1721881 has 4 divisors (see below), whose sum is σ = 1967872. Its totient is φ = 1475892.

The previous prime is 1721857. The next prime is 1721887. The reversal of 1721881 is 1881271.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1721881 - 2¹³ = 1713689 is a prime.

It is a super-2 number, since 2×1721881² = 5929748356322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1721887) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 122985 + ... + 122998.

It is an arithmetic number, because the mean of its divisors is an integer number (491968).

2^1721881 is an apocalyptic number.

It is an amenable number.

1721881 is a deficient number, since it is larger than the sum of its proper divisors (245991).

1721881 is an equidigital number, since it uses as much as digits as its factorization.

1721881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 245990.

The product of its digits is 896, while the sum is 28.

The square root of 1721881 is about 1312.2046334318. The cubic root of 1721881 is about 119.8581889611.

The spelling of 1721881 in words is "one million, seven hundred twenty-one thousand, eight hundred eighty-one".