1721520 has 80 divisors (see below), whose sum is σ = 5937120. Its totient is φ = 458496.

The previous prime is 1721513. The next prime is 1721521. The reversal of 1721520 is 251271.

It is a tau number, because it is divible by the number of its divisors (80).

It is a super-2 number, since 2×1721520² = 5927262220800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 1721493 and 1721502.

It is not an unprimeable number, because it can be changed into a prime (1721521) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1762 + ... + 2558.

It is an arithmetic number, because the mean of its divisors is an integer number (74214).

2^1721520 is an apocalyptic number.

1721520 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 1721520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2968560).

1721520 is an abundant number, since it is smaller than the sum of its proper divisors (4215600).

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

1721520 is a wasteful number, since it uses less digits than its factorization.

1721520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 819 (or 807 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 18.

The square root of 1721520 is about 1312.0670714563. The cubic root of 1721520 is about 119.8498121084.

Adding to 1721520 its reverse (251271), we get a palindrome (1972791).

The spelling of 1721520 in words is "one million, seven hundred twenty-one thousand, five hundred twenty".