851721 has 8 divisors (see below), whose sum is σ = 1223040. Its totient is φ = 524112.

The previous prime is 851689. The next prime is 851723. The reversal of 851721 is 127158.

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

It is not a de Polignac number, because 851721 - 2⁵ = 851689 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 851691 and 851700.

It is not an unprimeable number, because it can be changed into a prime (851723) 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, 10881 + ... + 10958.

It is an arithmetic number, because the mean of its divisors is an integer number (152880).

2⁸⁵¹⁷²¹ is an apocalyptic number.

It is an amenable number.

851721 is a deficient number, since it is larger than the sum of its proper divisors (371319).

851721 is a wasteful number, since it uses less digits than its factorization.

851721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21855.

The product of its digits is 560, while the sum is 24.

The square root of 851721 is about 922.8873170653. The cubic root of 851721 is about 94.7907119388.

Adding to 851721 its reverse (127158), we get a palindrome (978879).

The spelling of 851721 in words is "eight hundred fifty-one thousand, seven hundred twenty-one".