16780405 has 4 divisors (see below), whose sum is σ = 20136492. Its totient is φ = 13424320.

The previous prime is 16780399. The next prime is 16780417. The reversal of 16780405 is 50408761.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 50408761 = 13 ⋅3877597.

It can be written as a sum of positive squares in 2 ways, for example, as 11771761 + 5008644 = 3431^2 + 2238^2 .

It is not a de Polignac number, because 16780405 - 2¹¹ = 16778357 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1678036 + ... + 1678045.

It is an arithmetic number, because the mean of its divisors is an integer number (5034123).

Almost surely, 2^16780405 is an apocalyptic number.

It is an amenable number.

16780405 is a deficient number, since it is larger than the sum of its proper divisors (3356087).

16780405 is an equidigital number, since it uses as much as digits as its factorization.

16780405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3356086.

The product of its (nonzero) digits is 6720, while the sum is 31.

The square root of 16780405 is about 4096.3892637297. The cubic root of 16780405 is about 256.0162190652.

The spelling of 16780405 in words is "sixteen million, seven hundred eighty thousand, four hundred five".