1721391 has 8 divisors (see below), whose sum is σ = 2623104. Its totient is φ = 983640.

The previous prime is 1721383. The next prime is 1721407. The reversal of 1721391 is 1931271.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1721391 - 2³ = 1721383 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1721371) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40965 + ... + 41006.

It is an arithmetic number, because the mean of its divisors is an integer number (327888).

2^1721391 is an apocalyptic number.

1721391 is a deficient number, since it is larger than the sum of its proper divisors (901713).

1721391 is an equidigital number, since it uses as much as digits as its factorization.

1721391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81981.

The product of its digits is 378, while the sum is 24.

The square root of 1721391 is about 1312.0179114631. The cubic root of 1721391 is about 119.8468184338.

It can be divided in two parts, 1721 and 391, that added together give a palindrome (2112).

The spelling of 1721391 in words is "one million, seven hundred twenty-one thousand, three hundred ninety-one".