125821 has 2 divisors, whose sum is σ = 125822. Its totient is φ = 125820.

The previous prime is 125813. The next prime is 125863. The reversal of 125821 is 128521.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 98596 + 27225 = 314^2 + 165^2 .

It is an emirp because it is prime and its reverse (128521) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 125821 - 2³ = 125813 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (125221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 62910 + 62911.

It is an arithmetic number, because the mean of its divisors is an integer number (62911).

2¹²⁵⁸²¹ is an apocalyptic number.

It is an amenable number.

125821 is a deficient number, since it is larger than the sum of its proper divisors (1).

125821 is an equidigital number, since it uses as much as digits as its factorization.

125821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 160, while the sum is 19.

The square root of 125821 is about 354.7125596874. The cubic root of 125821 is about 50.1092278783.

It can be divided in two parts, 125 and 821, that added together give a triangular number (946 = T₄₃).

The spelling of 125821 in words is "one hundred twenty-five thousand, eight hundred twenty-one".