16557561 has 8 divisors (see below), whose sum is σ = 24529760. Its totient is φ = 11038356.

The previous prime is 16557533. The next prime is 16557577. The reversal of 16557561 is 16575561.

It is not a de Polignac number, because 16557561 - 2⁷ = 16557433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16557511) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 306595 + ... + 306648.

It is an arithmetic number, because the mean of its divisors is an integer number (3066220).

Almost surely, 2^16557561 is an apocalyptic number.

It is an amenable number.

16557561 is a deficient number, since it is larger than the sum of its proper divisors (7972199).

16557561 is an equidigital number, since it uses as much as digits as its factorization.

16557561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 613252 (or 613246 counting only the distinct ones).

The product of its digits is 31500, while the sum is 36.

The square root of 16557561 is about 4069.0983030642. The cubic root of 16557561 is about 254.8778653873.

It can be divided in two parts, 1655 and 7561, that added together give a square (9216 = 96²).

The spelling of 16557561 in words is "sixteen million, five hundred fifty-seven thousand, five hundred sixty-one".