75821 has 2 divisors, whose sum is σ = 75822. Its totient is φ = 75820.

The previous prime is 75797. The next prime is 75833. The reversal of 75821 is 12857.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 75625 + 196 = 275^2 + 14^2 .

It is a cyclic number.

It is not a de Polignac number, because 75821 - 2¹⁰ = 74797 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (75521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 37910 + 37911.

It is an arithmetic number, because the mean of its divisors is an integer number (37911).

2⁷⁵⁸²¹ is an apocalyptic number.

It is an amenable number.

75821 is a deficient number, since it is larger than the sum of its proper divisors (1).

75821 is an equidigital number, since it uses as much as digits as its factorization.

75821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 560, while the sum is 23.

The square root of 75821 is about 275.3561330350. The cubic root of 75821 is about 42.3249547695.

The spelling of 75821 in words is "seventy-five thousand, eight hundred twenty-one".