66421 has 4 divisors (see below), whose sum is σ = 67072. Its totient is φ = 65772.

The previous prime is 66413. The next prime is 66431. The reversal of 66421 is 12466.

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 a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 66421 - 2³ = 66413 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66431) 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, 135 + ... + 388.

It is an arithmetic number, because the mean of its divisors is an integer number (16768).

2⁶⁶⁴²¹ is an apocalyptic number.

It is an amenable number.

66421 is a deficient number, since it is larger than the sum of its proper divisors (651).

66421 is a wasteful number, since it uses less digits than its factorization.

66421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 650.

The product of its digits is 288, while the sum is 19.

The square root of 66421 is about 257.7227192158. The cubic root of 66421 is about 40.4981455230.

Adding to 66421 its reverse (12466), we get a palindrome (78887).

The spelling of 66421 in words is "sixty-six thousand, four hundred twenty-one".