667728409 has 2 divisors, whose sum is σ = 667728410. Its totient is φ = 667728408.

The previous prime is 667728407. The next prime is 667728491. The reversal of 667728409 is 904827766.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 653927184 + 13801225 = 25572^2 + 3715^2 .

It is a cyclic number.

It is not a de Polignac number, because 667728409 - 2¹ = 667728407 is a prime.

It is a super-2 number, since 2×667728409² = 891722456371342562, which contains 22 as substring.

Together with 667728407, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (667728403) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333864204 + 333864205.

It is an arithmetic number, because the mean of its divisors is an integer number (333864205).

Almost surely, 2^667728409 is an apocalyptic number.

It is an amenable number.

667728409 is a deficient number, since it is larger than the sum of its proper divisors (1).

667728409 is an equidigital number, since it uses as much as digits as its factorization.

667728409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1016064, while the sum is 49.

The square root of 667728409 is about 25840.4413468501. The cubic root of 667728409 is about 874.0439774383.

The spelling of 667728409 in words is "six hundred sixty-seven million, seven hundred twenty-eight thousand, four hundred nine".