15505561 has 2 divisors, whose sum is σ = 15505562. Its totient is φ = 15505560.

The previous prime is 15505543. The next prime is 15505573. The reversal of 15505561 is 16550551.

15505561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11095561 + 4410000 = 3331^2 + 2100^2 .

It is a cyclic number.

It is not a de Polignac number, because 15505561 - 2⁷ = 15505433 is a prime.

It is not a weakly prime, because it can be changed into another prime (15505541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7752780 + 7752781.

It is an arithmetic number, because the mean of its divisors is an integer number (7752781).

Almost surely, 2^15505561 is an apocalyptic number.

It is an amenable number.

15505561 is a deficient number, since it is larger than the sum of its proper divisors (1).

15505561 is an equidigital number, since it uses as much as digits as its factorization.

15505561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3750, while the sum is 28.

The square root of 15505561 is about 3937.7101213777. The cubic root of 15505561 is about 249.3613619550.

The spelling of 15505561 in words is "fifteen million, five hundred five thousand, five hundred sixty-one".