126561 has 4 divisors (see below), whose sum is σ = 168752. Its totient is φ = 84372.

The previous prime is 126551. The next prime is 126583. The reversal of 126561 is 165621.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 165621 = 3 ⋅55207.

It is not a de Polignac number, because 126561 - 2⁷ = 126433 is a prime.

It is a D-number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (126541) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21091 + ... + 21096.

It is an arithmetic number, because the mean of its divisors is an integer number (42188).

2¹²⁶⁵⁶¹ is an apocalyptic number.

It is an amenable number.

126561 is a deficient number, since it is larger than the sum of its proper divisors (42191).

126561 is an equidigital number, since it uses as much as digits as its factorization.

126561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42190.

The product of its digits is 360, while the sum is 21.

The square root of 126561 is about 355.7541285776. The cubic root of 126561 is about 50.2072729049.

Subtracting 126561 from its reverse (165621), we obtain a triangular number (39060 = T₂₇₉).

It can be divided in two parts, 1265 and 61, that added together give a triangular number (1326 = T₅₁).

The spelling of 126561 in words is "one hundred twenty-six thousand, five hundred sixty-one".