161216809 has 4 divisors (see below), whose sum is σ = 173618116. Its totient is φ = 148815504.

The previous prime is 161216779. The next prime is 161216819. The reversal of 161216809 is 908612161.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 908612161 = 4783 ⋅189967.

It can be written as a sum of positive squares in 2 ways, for example, as 35664784 + 125552025 = 5972^2 + 11205^2 .

It is a cyclic number.

It is not a de Polignac number, because 161216809 - 2¹⁷ = 161085737 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161216819) 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, 6200634 + ... + 6200659.

It is an arithmetic number, because the mean of its divisors is an integer number (43404529).

Almost surely, 2^161216809 is an apocalyptic number.

It is an amenable number.

161216809 is a deficient number, since it is larger than the sum of its proper divisors (12401307).

161216809 is a wasteful number, since it uses less digits than its factorization.

161216809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12401306.

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 161216809 is about 12697.1181375933. The cubic root of 161216809 is about 544.2562691521.

The spelling of 161216809 in words is "one hundred sixty-one million, two hundred sixteen thousand, eight hundred nine".