165221405 has 8 divisors (see below), whose sum is σ = 202006872. Its totient is φ = 129683008.

The previous prime is 165221387. The next prime is 165221423. The reversal of 165221405 is 504122561.

It is an interprime number because it is at equal distance from previous prime (165221387) and next prime (165221423).

It can be written as a sum of positive squares in 4 ways, for example, as 15452761 + 149768644 = 3931^2 + 12238^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 165221405 - 2⁶ = 165221341 is a prime.

It is a super-2 number, since 2×165221405² = 54596225340348050, which contains 22 as substring.

It is a Duffinian number.

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 7 ways as a sum of consecutive naturals, for example, 311474 + ... + 312003.

It is an arithmetic number, because the mean of its divisors is an integer number (25250859).

Almost surely, 2^165221405 is an apocalyptic number.

It is an amenable number.

165221405 is a deficient number, since it is larger than the sum of its proper divisors (36785467).

165221405 is an equidigital number, since it uses as much as digits as its factorization.

165221405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 623535.

The product of its (nonzero) digits is 2400, while the sum is 26.

The square root of 165221405 is about 12853.8478674675. The cubic root of 165221405 is about 548.7258715736.

Adding to 165221405 its reverse (504122561), we get a palindrome (669343966).

The spelling of 165221405 in words is "one hundred sixty-five million, two hundred twenty-one thousand, four hundred five".