155561 has 8 divisors (see below), whose sum is σ = 180864. Its totient is φ = 131040.

The previous prime is 155557. The next prime is 155569. The reversal of 155561 is 165551.

155561 is nontrivially palindromic in base 11.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 155561 - 2² = 155557 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 155561.

It is not an unprimeable number, because it can be changed into a prime (155569) 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 7 ways as a sum of consecutive naturals, for example, 341 + ... + 653.

It is an arithmetic number, because the mean of its divisors is an integer number (22608).

2¹⁵⁵⁵⁶¹ is an apocalyptic number.

It is an amenable number.

155561 is a deficient number, since it is larger than the sum of its proper divisors (25303).

155561 is an equidigital number, since it uses as much as digits as its factorization.

155561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 391.

The product of its digits is 750, while the sum is 23.

The square root of 155561 is about 394.4122209060. The cubic root of 155561 is about 53.7815823046.

The spelling of 155561 in words is "one hundred fifty-five thousand, five hundred sixty-one".