155503561 has 4 divisors (see below), whose sum is σ = 157693824. Its totient is φ = 153313300.

The previous prime is 155503549. The next prime is 155503577. The reversal of 155503561 is 165305551.

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: 165305551 = 59 ⋅2801789.

It is a cyclic number.

It is not a de Polignac number, because 155503561 - 2¹⁵ = 155470793 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (155503591) 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 in 3 ways as a sum of consecutive naturals, for example, 1095025 + ... + 1095166.

It is an arithmetic number, because the mean of its divisors is an integer number (39423456).

Almost surely, 2^155503561 is an apocalyptic number.

It is an amenable number.

155503561 is a deficient number, since it is larger than the sum of its proper divisors (2190263).

155503561 is an equidigital number, since it uses as much as digits as its factorization.

155503561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2190262.

The product of its (nonzero) digits is 11250, while the sum is 31.

The square root of 155503561 is about 12470.1066956141. The cubic root of 155503561 is about 537.7496209221.

The spelling of 155503561 in words is "one hundred fifty-five million, five hundred three thousand, five hundred sixty-one".