165407721 has 8 divisors (see below), whose sum is σ = 222280704. Its totient is φ = 109403280.

The previous prime is 165407717. The next prime is 165407741. The reversal of 165407721 is 127704561.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 165407721 - 2² = 165407717 is a prime.

It is not an unprimeable number, because it can be changed into a prime (165407741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 216690 + ... + 217451.

It is an arithmetic number, because the mean of its divisors is an integer number (27785088).

Almost surely, 2^165407721 is an apocalyptic number.

It is an amenable number.

165407721 is a deficient number, since it is larger than the sum of its proper divisors (56872983).

165407721 is a wasteful number, since it uses less digits than its factorization.

165407721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 434271.

The product of its (nonzero) digits is 11760, while the sum is 33.

The square root of 165407721 is about 12861.0933050033. The cubic root of 165407721 is about 548.9320555196.

The spelling of 165407721 in words is "one hundred sixty-five million, four hundred seven thousand, seven hundred twenty-one".