681921 has 12 divisors (see below), whose sum is σ = 1043172. Its totient is φ = 427776.

The previous prime is 681913. The next prime is 681931. The reversal of 681921 is 129186.

681921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 505521 + 176400 = 711^2 + 420^2 .

It is not a de Polignac number, because 681921 - 2³ = 681913 is a prime.

It is not an unprimeable number, because it can be changed into a prime (681931) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2076 + ... + 2381.

It is an arithmetic number, because the mean of its divisors is an integer number (86931).

2⁶⁸¹⁹²¹ is an apocalyptic number.

It is an amenable number.

681921 is a deficient number, since it is larger than the sum of its proper divisors (361251).

681921 is a wasteful number, since it uses less digits than its factorization.

681921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4480 (or 4477 counting only the distinct ones).

The product of its digits is 864, while the sum is 27.

The square root of 681921 is about 825.7850809987. The cubic root of 681921 is about 88.0193225476.

The spelling of 681921 in words is "six hundred eighty-one thousand, nine hundred twenty-one".