165721849 has 4 divisors (see below), whose sum is σ = 165760000. Its totient is φ = 165683700.

The previous prime is 165721847. The next prime is 165721861. The reversal of 165721849 is 948127561.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 948127561 = 233 ⋅4069217.

It is a cyclic number.

It is not a de Polignac number, because 165721849 - 2¹ = 165721847 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165721841) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11577 + ... + 21574.

It is an arithmetic number, because the mean of its divisors is an integer number (41440000).

Almost surely, 2^165721849 is an apocalyptic number.

It is an amenable number.

165721849 is a deficient number, since it is larger than the sum of its proper divisors (38151).

165721849 is an equidigital number, since it uses as much as digits as its factorization.

165721849 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38150.

The product of its digits is 120960, while the sum is 43.

The square root of 165721849 is about 12873.2998489121. The cubic root of 165721849 is about 549.2793304934.

The spelling of 165721849 in words is "one hundred sixty-five million, seven hundred twenty-one thousand, eight hundred forty-nine".