823721 has 2 divisors, whose sum is σ = 823722. Its totient is φ = 823720.

The previous prime is 823717. The next prime is 823723. The reversal of 823721 is 127328.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 672400 + 151321 = 820^2 + 389^2 .

It is a cyclic number.

It is not a de Polignac number, because 823721 - 2² = 823717 is a prime.

Together with 823723, it forms a pair of twin primes.

It is a Chen prime.

It is a d-powerful number, because it can be written as 8 + 2⁵ + 7⁷ + 3² + 2⁷ + 1 .

It is not a weakly prime, because it can be changed into another prime (823723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 411860 + 411861.

It is an arithmetic number, because the mean of its divisors is an integer number (411861).

2⁸²³⁷²¹ is an apocalyptic number.

It is an amenable number.

823721 is a deficient number, since it is larger than the sum of its proper divisors (1).

823721 is an equidigital number, since it uses as much as digits as its factorization.

823721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 672, while the sum is 23.

The square root of 823721 is about 907.5907668107. The cubic root of 823721 is about 93.7403806427.

The spelling of 823721 in words is "eight hundred twenty-three thousand, seven hundred twenty-one".