665421 has 4 divisors (see below), whose sum is σ = 887232. Its totient is φ = 443612.

The previous prime is 665419. The next prime is 665429. The reversal of 665421 is 124566.

665421 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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.

It is a cyclic number.

It is not a de Polignac number, because 665421 - 2¹ = 665419 is a prime.

It is a D-number.

It is a Curzon number.

665421 is a lucky number.

It is a nialpdrome in base 10.

It is a junction number, because it is equal to n+sod(n) for n = 665391 and 665400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665429) 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, 110901 + ... + 110906.

It is an arithmetic number, because the mean of its divisors is an integer number (221808).

2⁶⁶⁵⁴²¹ is an apocalyptic number.

It is an amenable number.

665421 is a deficient number, since it is larger than the sum of its proper divisors (221811).

665421 is a wasteful number, since it uses less digits than its factorization.

665421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221810.

The product of its digits is 1440, while the sum is 24.

The square root of 665421 is about 815.7334123352. The cubic root of 665421 is about 87.3036030471.

Adding to 665421 its reverse (124566), we get a palindrome (789987).

The spelling of 665421 in words is "six hundred sixty-five thousand, four hundred twenty-one".