161555905 has 16 divisors (see below), whose sum is σ = 221950080. Its totient is φ = 110587392.

The previous prime is 161555833. The next prime is 161555921. The reversal of 161555905 is 509555161.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 161555905 - 2²⁵ = 128001473 is a prime.

It is a super-2 number, since 2×161555905² = 52200620880738050, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17937 + ... + 25393.

It is an arithmetic number, because the mean of its divisors is an integer number (13871880).

Almost surely, 2^161555905 is an apocalyptic number.

It is an amenable number.

161555905 is a deficient number, since it is larger than the sum of its proper divisors (60394175).

161555905 is an equidigital number, since it uses as much as digits as its factorization.

161555905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8088.

The product of its (nonzero) digits is 33750, while the sum is 37.

The square root of 161555905 is about 12710.4643896279. The cubic root of 161555905 is about 544.6375897705.

The spelling of 161555905 in words is "one hundred sixty-one million, five hundred fifty-five thousand, nine hundred five".