161817381 has 48 divisors (see below), whose sum is σ = 264176640. Its totient is φ = 94601760.

The previous prime is 161817379. The next prime is 161817451. The reversal of 161817381 is 183718161.

It is a happy number.

161817381 is a `hidden beast` number, since 1 + 618 + 1 + 7 + 38 + 1 = 666.

It is not a de Polignac number, because 161817381 - 2¹ = 161817379 is a prime.

It is a super-2 number, since 2×161817381² = 52369729587398322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161817371) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 385990 + ... + 386408.

It is an arithmetic number, because the mean of its divisors is an integer number (5503680).

Almost surely, 2^161817381 is an apocalyptic number.

161817381 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

161817381 is a deficient number, since it is larger than the sum of its proper divisors (102359259).

161817381 is a wasteful number, since it uses less digits than its factorization.

161817381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 566 (or 563 counting only the distinct ones).

The product of its digits is 8064, while the sum is 36.

The square root of 161817381 is about 12720.7460866099. The cubic root of 161817381 is about 544.9312608645.

The spelling of 161817381 in words is "one hundred sixty-one million, eight hundred seventeen thousand, three hundred eighty-one".