16655501561 has 4 divisors (see below), whose sum is σ = 16658742672. Its totient is φ = 16652260452.

The previous prime is 16655501557. The next prime is 16655501609. The reversal of 16655501561 is 16510555661.

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: 16510555661 = 75511 ⋅218651.

It is a cyclic number.

It is not a de Polignac number, because 16655501561 - 2² = 16655501557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16655501501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1612835 + ... + 1623128.

It is an arithmetic number, because the mean of its divisors is an integer number (4164685668).

Almost surely, 2^16655501561 is an apocalyptic number.

It is an amenable number.

16655501561 is a deficient number, since it is larger than the sum of its proper divisors (3241111).

16655501561 is an equidigital number, since it uses as much as digits as its factorization.

16655501561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3241110.

The product of its (nonzero) digits is 135000, while the sum is 41.

The spelling of 16655501561 in words is "sixteen billion, six hundred fifty-five million, five hundred one thousand, five hundred sixty-one".