681988 has 6 divisors (see below), whose sum is σ = 1193486. Its totient is φ = 340992.

The previous prime is 681983. The next prime is 681997. The reversal of 681988 is 889186.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 515524 + 166464 = 718^2 + 408^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 681988.

It is not an unprimeable number, because it can be changed into a prime (681983) by changing a digit.

681988 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 85245 + ... + 85252.

2⁶⁸¹⁹⁸⁸ is an apocalyptic number.

It is an amenable number.

681988 is a deficient number, since it is larger than the sum of its proper divisors (511498).

681988 is a wasteful number, since it uses less digits than its factorization.

681988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 170501 (or 170499 counting only the distinct ones).

The product of its digits is 27648, while the sum is 40.

The square root of 681988 is about 825.8256474583. The cubic root of 681988 is about 88.0222051403.

The spelling of 681988 in words is "six hundred eighty-one thousand, nine hundred eighty-eight".