1661680 has 20 divisors (see below), whose sum is σ = 3863592. Its totient is φ = 664640.

The previous prime is 1661677. The next prime is 1661713. The reversal of 1661680 is 861661.

It is a tau number, because it is divible by the number of its divisors (20).

It is a super-2 number, since 2×1661680² = 5522360844800, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10306 + ... + 10465.

2^1661680 is an apocalyptic number.

1661680 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1661680 is an abundant number, since it is smaller than the sum of its proper divisors (2201912).

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

1661680 is a wasteful number, since it uses less digits than its factorization.

1661680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20784 (or 20778 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 1661680 is about 1289.0616742422. The cubic root of 1661680 is about 118.4447450798. Note that the first 3 decimals are identical.

The spelling of 1661680 in words is "one million, six hundred sixty-one thousand, six hundred eighty".