1661664 has 48 divisors (see below), whose sum is σ = 4596480. Its totient is φ = 524160.

The previous prime is 1661663. The next prime is 1661669. The reversal of 1661664 is 4661661.

It is a tau number, because it is divible by the number of its divisors (48).

It is a super-2 number, since 2×1661664² = 5522254497792, which contains 22 as substring.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661663) 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, 1369 + ... + 2279.

It is an arithmetic number, because the mean of its divisors is an integer number (95760).

2^1661664 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1661664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2298240).

1661664 is an abundant number, since it is smaller than the sum of its proper divisors (2934816).

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

1661664 is a wasteful number, since it uses less digits than its factorization.

1661664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 943 (or 935 counting only the distinct ones).

The product of its digits is 5184, while the sum is 30.

The square root of 1661664 is about 1289.0554681626. The cubic root of 1661664 is about 118.4443649179. Note that the first 3 decimals are identical.

It can be divided in two parts, 166 and 1664, that added together give a triangular number (1830 = T₆₀).

The spelling of 1661664 in words is "one million, six hundred sixty-one thousand, six hundred sixty-four".