16381561 has 4 divisors (see below), whose sum is σ = 18721792. Its totient is φ = 14041332.

The previous prime is 16381513. The next prime is 16381577. The reversal of 16381561 is 16518361.

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.

It is a cyclic number.

It is not a de Polignac number, because 16381561 - 2¹³ = 16373369 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16381061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1170105 + ... + 1170118.

It is an arithmetic number, because the mean of its divisors is an integer number (4680448).

Almost surely, 2^16381561 is an apocalyptic number.

It is an amenable number.

16381561 is a deficient number, since it is larger than the sum of its proper divisors (2340231).

16381561 is an equidigital number, since it uses as much as digits as its factorization.

16381561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2340230.

The product of its digits is 4320, while the sum is 31.

The square root of 16381561 is about 4047.4141127391. The cubic root of 16381561 is about 253.9715645932.

The spelling of 16381561 in words is "sixteen million, three hundred eighty-one thousand, five hundred sixty-one".