1661320 has 32 divisors (see below), whose sum is σ = 3832920. Its totient is φ = 647680.

The previous prime is 1661311. The next prime is 1661327. The reversal of 1661320 is 231661.

It can be written as a sum of positive squares in 4 ways, for example, as 320356 + 1340964 = 566^2 + 1158^2 .

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (1661327) 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, 1134 + ... + 2146.

2^1661320 is an apocalyptic number.

1661320 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 1661320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1916460).

1661320 is an abundant number, since it is smaller than the sum of its proper divisors (2171600).

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

1661320 is a wasteful number, since it uses less digits than its factorization.

1661320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1065 (or 1061 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 19.

The square root of 1661320 is about 1288.9220302253. The cubic root of 1661320 is about 118.4361908479.

Adding to 1661320 its reverse (231661), we get a palindrome (1892981).

The spelling of 1661320 in words is "one million, six hundred sixty-one thousand, three hundred twenty".