855721 has 2 divisors, whose sum is σ = 855722. Its totient is φ = 855720.

The previous prime is 855719. The next prime is 855727. The reversal of 855721 is 127558.

855721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 837225 + 18496 = 915^2 + 136^2 .

It is a cyclic number.

It is not a de Polignac number, because 855721 - 2¹ = 855719 is a prime.

Together with 855719, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 855721.

It is not a weakly prime, because it can be changed into another prime (855727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 427860 + 427861.

It is an arithmetic number, because the mean of its divisors is an integer number (427861).

2⁸⁵⁵⁷²¹ is an apocalyptic number.

It is an amenable number.

855721 is a deficient number, since it is larger than the sum of its proper divisors (1).

855721 is an equidigital number, since it uses as much as digits as its factorization.

855721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2800, while the sum is 28.

The square root of 855721 is about 925.0518904364. The cubic root of 855721 is about 94.9388711083.

The spelling of 855721 in words is "eight hundred fifty-five thousand, seven hundred twenty-one".