1681664 has 18 divisors (see below), whose sum is σ = 3357270. Its totient is φ = 840704.

The previous prime is 1681661. The next prime is 1681679. The reversal of 1681664 is 4661861.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 1638400 + 43264 = 1280^2 + 208^2 .

It is a Harshad number since it is a multiple of its sum of digits (32).

It is an Ulam number.

It is a self number, because there is not a number n which added to its sum of digits gives 1681664.

It is not an unprimeable number, because it can be changed into a prime (1681661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3029 + ... + 3540.

It is an arithmetic number, because the mean of its divisors is an integer number (186515).

2^1681664 is an apocalyptic number.

It is an amenable number.

1681664 is a deficient number, since it is larger than the sum of its proper divisors (1675606).

1681664 is an frugal number, since it uses more digits than its factorization.

1681664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6585 (or 6571 counting only the distinct ones).

The product of its digits is 6912, while the sum is 32.

The square root of 1681664 is about 1296.7898827489. The cubic root of 1681664 is about 118.9176748586.

The spelling of 1681664 in words is "one million, six hundred eighty-one thousand, six hundred sixty-four".