161551209 has 4 divisors (see below), whose sum is σ = 215401616. Its totient is φ = 107700804.

The previous prime is 161551207. The next prime is 161551211. The reversal of 161551209 is 902155161.

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: 902155161 = 3 ⋅300718387.

It is an interprime number because it is at equal distance from previous prime (161551207) and next prime (161551211).

It is not a de Polignac number, because 161551209 - 2¹ = 161551207 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (161551207) 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, 26925199 + ... + 26925204.

It is an arithmetic number, because the mean of its divisors is an integer number (53850404).

Almost surely, 2^161551209 is an apocalyptic number.

It is an amenable number.

161551209 is a deficient number, since it is larger than the sum of its proper divisors (53850407).

161551209 is an equidigital number, since it uses as much as digits as its factorization.

161551209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53850406.

The product of its (nonzero) digits is 2700, while the sum is 30.

The square root of 161551209 is about 12710.2796586070. The cubic root of 161551209 is about 544.6323126645.

The spelling of 161551209 in words is "one hundred sixty-one million, five hundred fifty-one thousand, two hundred nine".