165193721 has 16 divisors (see below), whose sum is σ = 207163008. Its totient is φ = 127968000.

The previous prime is 165193711. The next prime is 165193723. The reversal of 165193721 is 127391561.

It is a cyclic number.

It is not a de Polignac number, because 165193721 - 2¹⁸ = 164931577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165193723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7121 + ... + 19521.

It is an arithmetic number, because the mean of its divisors is an integer number (12947688).

Almost surely, 2^165193721 is an apocalyptic number.

165193721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

165193721 is a deficient number, since it is larger than the sum of its proper divisors (41969287).

165193721 is a wasteful number, since it uses less digits than its factorization.

165193721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12592.

The product of its digits is 11340, while the sum is 35.

The square root of 165193721 is about 12852.7709463757. The cubic root of 165193721 is about 548.6952222447.

The spelling of 165193721 in words is "one hundred sixty-five million, one hundred ninety-three thousand, seven hundred twenty-one".