667921 has 2 divisors, whose sum is σ = 667922. Its totient is φ = 667920.

The previous prime is 667903. The next prime is 667949. The reversal of 667921 is 129766.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 555025 + 112896 = 745^2 + 336^2 .

It is a cyclic number.

It is not a de Polignac number, because 667921 - 2¹⁷ = 536849 is a prime.

It is a super-2 number, since 2×667921² = 892236924482, which contains 22 as substring.

It is an Ulam number.

It is a nialpdrome in base 16.

It is not a weakly prime, because it can be changed into another prime (667991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333960 + 333961.

It is an arithmetic number, because the mean of its divisors is an integer number (333961).

2⁶⁶⁷⁹²¹ is an apocalyptic number.

It is an amenable number.

667921 is a deficient number, since it is larger than the sum of its proper divisors (1).

667921 is an equidigital number, since it uses as much as digits as its factorization.

667921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4536, while the sum is 31.

The square root of 667921 is about 817.2643391217. The cubic root of 667921 is about 87.4128002031.

The spelling of 667921 in words is "six hundred sixty-seven thousand, nine hundred twenty-one".