165221406 has 48 divisors (see below), whose sum is σ = 410892768. Its totient is φ = 47001600.

The previous prime is 165221387. The next prime is 165221423. The reversal of 165221406 is 604122561.

165221406 is a `hidden beast` number, since 1 + 652 + 2 + 1 + 4 + 0 + 6 = 666.

It is a super-3 number, since 3×165221406³ (a number of 26 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a self number, because there is not a number n which added to its sum of digits gives 165221406.

It is a congruent number.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 27646 + ... + 33086.

It is an arithmetic number, because the mean of its divisors is an integer number (8560266).

Almost surely, 2^165221406 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 165221406, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (205446384).

165221406 is an abundant number, since it is smaller than the sum of its proper divisors (245671362).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

165221406 is a wasteful number, since it uses less digits than its factorization.

165221406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5697 (or 5694 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 165221406 is about 12853.8479063664. The cubic root of 165221406 is about 548.7258726807.

Adding to 165221406 its reverse (604122561), we get a palindrome (769343967).

The spelling of 165221406 in words is "one hundred sixty-five million, two hundred twenty-one thousand, four hundred six".