681664 has 14 divisors (see below), whose sum is σ = 1352804. Its totient is φ = 340800.

The previous prime is 681647. The next prime is 681673. The reversal of 681664 is 466186.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5262 + ... + 5389.

2⁶⁸¹⁶⁶⁴ is an apocalyptic number.

681664 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

681664 is a deficient number, since it is larger than the sum of its proper divisors (671140).

681664 is a wasteful number, since it uses less digits than its factorization.

681664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10663 (or 10653 counting only the distinct ones).

The product of its digits is 6912, while the sum is 31.

The square root of 681664 is about 825.6294568388. The cubic root of 681664 is about 88.0082636868.

It can be divided in two parts, 6 and 81664, that multiplied together give a palindrome (489984).

The spelling of 681664 in words is "six hundred eighty-one thousand, six hundred sixty-four".