161391555 has 32 divisors (see below), whose sum is σ = 308992320. Its totient is φ = 79453440.

The previous prime is 161391551. The next prime is 161391563. The reversal of 161391555 is 555193161.

161391555 is a `hidden beast` number, since 1 + 6 + 13 + 91 + 555 = 666.

It is not a de Polignac number, because 161391555 - 2² = 161391551 is a prime.

It is not an unprimeable number, because it can be changed into a prime (161391551) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 44226 + ... + 47735.

It is an arithmetic number, because the mean of its divisors is an integer number (9656010).

Almost surely, 2^161391555 is an apocalyptic number.

161391555 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

161391555 is a deficient number, since it is larger than the sum of its proper divisors (147600765).

161391555 is a wasteful number, since it uses less digits than its factorization.

161391555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91988 (or 91982 counting only the distinct ones).

The product of its digits is 20250, while the sum is 36.

The square root of 161391555 is about 12703.9975991811. The cubic root of 161391555 is about 544.4528414257.

The spelling of 161391555 in words is "one hundred sixty-one million, three hundred ninety-one thousand, five hundred fifty-five".