165681387 has 12 divisors (see below), whose sum is σ = 251913480. Its totient is φ = 104640768.

The previous prime is 165681359. The next prime is 165681403. The reversal of 165681387 is 783186561.

165681387 is a `hidden beast` number, since 1 + 6 + 568 + 1 + 3 + 87 = 666.

It is not a de Polignac number, because 165681387 - 2⁶ = 165681323 is a prime.

It is not an unprimeable number, because it can be changed into a prime (165681487) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 484278 + ... + 484619.

It is an arithmetic number, because the mean of its divisors is an integer number (20992790).

Almost surely, 2^165681387 is an apocalyptic number.

165681387 is a deficient number, since it is larger than the sum of its proper divisors (86232093).

165681387 is a wasteful number, since it uses less digits than its factorization.

165681387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 968922 (or 968919 counting only the distinct ones).

The product of its digits is 241920, while the sum is 45.

The square root of 165681387 is about 12871.7282056451. The cubic root of 165681387 is about 549.2346235554.

It can be divided in two parts, 16568 and 1387, that added together give a triangular number (17955 = T₁₈₉).

The spelling of 165681387 in words is "one hundred sixty-five million, six hundred eighty-one thousand, three hundred eighty-seven".