16561555 has 8 divisors (see below), whose sum is σ = 19921392. Its totient is φ = 13217568.

The previous prime is 16561549. The next prime is 16561577. The reversal of 16561555 is 55516561.

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

It is a cyclic number.

It is not a de Polignac number, because 16561555 - 2³ = 16561547 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 16561555.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1524 + ... + 5953.

It is an arithmetic number, because the mean of its divisors is an integer number (2490174).

Almost surely, 2^16561555 is an apocalyptic number.

16561555 is a deficient number, since it is larger than the sum of its proper divisors (3359837).

16561555 is an equidigital number, since it uses as much as digits as its factorization.

16561555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7925.

The product of its digits is 22500, while the sum is 34.

The square root of 16561555 is about 4069.5890455917. The cubic root of 16561555 is about 254.8983575429.

The spelling of 16561555 in words is "sixteen million, five hundred sixty-one thousand, five hundred fifty-five".