15555561 has 16 divisors (see below), whose sum is σ = 25098624. Its totient is φ = 8365824.

The previous prime is 15555559. The next prime is 15555563. The reversal of 15555561 is 16555551.

It is an interprime number because it is at equal distance from previous prime (15555559) and next prime (15555563).

It is not a de Polignac number, because 15555561 - 2¹ = 15555559 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (15555563) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21430 + ... + 22143.

It is an arithmetic number, because the mean of its divisors is an integer number (1568664).

Almost surely, 2^15555561 is an apocalyptic number.

It is an amenable number.

15555561 is a deficient number, since it is larger than the sum of its proper divisors (9543063).

15555561 is a wasteful number, since it uses less digits than its factorization.

15555561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43600.

The product of its digits is 18750, while the sum is 33.

The square root of 15555561 is about 3944.0538789423. The cubic root of 15555561 is about 249.6291086973.

The spelling of 15555561 in words is "fifteen million, five hundred fifty-five thousand, five hundred sixty-one".