125561 has 4 divisors (see below), whose sum is σ = 126324. Its totient is φ = 124800.

The previous prime is 125551. The next prime is 125591. The reversal of 125561 is 165521.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 165521 = 103 ⋅1607.

It can be written as a sum of positive squares in 2 ways, for example, as 65536 + 60025 = 256^2 + 245^2 .

It is a cyclic number.

It is not a de Polignac number, because 125561 - 2⁶ = 125497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (125551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20 + ... + 501.

It is an arithmetic number, because the mean of its divisors is an integer number (31581).

2¹²⁵⁵⁶¹ is an apocalyptic number.

It is an amenable number.

125561 is a deficient number, since it is larger than the sum of its proper divisors (763).

125561 is an equidigital number, since it uses as much as digits as its factorization.

125561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 762.

The product of its digits is 300, while the sum is 20.

The square root of 125561 is about 354.3458762283. The cubic root of 125561 is about 50.0746883774.

It can be divided in two parts, 125 and 561, that multiplied together give a triangular number (70125 = T₃₇₄).

The spelling of 125561 in words is "one hundred twenty-five thousand, five hundred sixty-one".