165720681 has 64 divisors (see below), whose sum is σ = 297676800. Its totient is φ = 89071488.

The previous prime is 165720677. The next prime is 165720683. The reversal of 165720681 is 186027561.

165720681 is a `hidden beast` number, since 1 + 6 + 572 + 0 + 6 + 81 = 666.

It is not a de Polignac number, because 165720681 - 2² = 165720677 is a prime.

It is a super-2 number, since 2×165720681² = 54926688222207522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (165720683) 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 63 ways as a sum of consecutive naturals, for example, 290965 + ... + 291533.

It is an arithmetic number, because the mean of its divisors is an integer number (4651200).

Almost surely, 2^165720681 is an apocalyptic number.

It is an amenable number.

165720681 is a deficient number, since it is larger than the sum of its proper divisors (131956119).

165720681 is a wasteful number, since it uses less digits than its factorization.

165720681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 675 (or 669 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 165720681 is about 12873.2544836184. The cubic root of 165720681 is about 549.2780400586.

The spelling of 165720681 in words is "one hundred sixty-five million, seven hundred twenty thousand, six hundred eighty-one".