681821 has 8 divisors (see below), whose sum is σ = 784320. Its totient is φ = 580608.

The previous prime is 681809. The next prime is 681823. The reversal of 681821 is 128186.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-681821 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681823) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1610 + ... + 1988.

It is an arithmetic number, because the mean of its divisors is an integer number (98040).

2⁶⁸¹⁸²¹ is an apocalyptic number.

It is an amenable number.

681821 is a deficient number, since it is larger than the sum of its proper divisors (102499).

681821 is a wasteful number, since it uses less digits than its factorization.

681821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 643.

The product of its digits is 768, while the sum is 26.

The square root of 681821 is about 825.7245303368. The cubic root of 681821 is about 88.0150198192.

The spelling of 681821 in words is "six hundred eighty-one thousand, eight hundred twenty-one".