667421 has 2 divisors, whose sum is σ = 667422. Its totient is φ = 667420.

The previous prime is 667417. The next prime is 667423. The reversal of 667421 is 124766.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 403225 + 264196 = 635^2 + 514^2 .

It is a cyclic number.

It is not a de Polignac number, because 667421 - 2² = 667417 is a prime.

Together with 667423, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (667423) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333710 + 333711.

It is an arithmetic number, because the mean of its divisors is an integer number (333711).

2⁶⁶⁷⁴²¹ is an apocalyptic number.

It is an amenable number.

667421 is a deficient number, since it is larger than the sum of its proper divisors (1).

667421 is an equidigital number, since it uses as much as digits as its factorization.

667421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2016, while the sum is 26.

The square root of 667421 is about 816.9583832730. The cubic root of 667421 is about 87.3909825975.

The spelling of 667421 in words is "six hundred sixty-seven thousand, four hundred twenty-one".