1664640 has 144 divisors (see below), whose sum is σ = 6106230. Its totient is φ = 417792.

The previous prime is 1664633. The next prime is 1664651. The reversal of 1664640 is 464661.

1664640 is a `hidden beast` number, since 16 + 6 + 4 + 640 = 666.

1664640 is nontrivially palindromic in base 11.

It can be written as a sum of positive squares in 3 ways, for example, as 1617984 + 46656 = 1272^2 + 216^2 .

It is a tau number, because it is divible by the number of its divisors (144).

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 97912 + ... + 97928.

2^1664640 is an apocalyptic number.

1664640 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 1664640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3053115).

1664640 is an abundant number, since it is smaller than the sum of its proper divisors (4441590).

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

1664640 is a wasteful number, since it uses less digits than its factorization.

1664640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59 (or 27 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 1664640 is about 1290.2092853487. The cubic root of 1664640 is about 118.5150330765.

It can be divided in two parts, 1664 and 640, that added together give a square (2304 = 48²).

The spelling of 1664640 in words is "one million, six hundred sixty-four thousand, six hundred forty".