640672667 has 2 divisors, whose sum is σ = 640672668. Its totient is φ = 640672666.

The previous prime is 640672657. The next prime is 640672673. The reversal of 640672667 is 766276046.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 640672667 - 2¹⁰ = 640671643 is a prime.

It is a super-2 number, since 2×640672667² = 820922932481785778, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (640672607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320336333 + 320336334.

It is an arithmetic number, because the mean of its divisors is an integer number (320336334).

Almost surely, 2^640672667 is an apocalyptic number.

640672667 is a deficient number, since it is larger than the sum of its proper divisors (1).

640672667 is an equidigital number, since it uses as much as digits as its factorization.

640672667 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 508032, while the sum is 44.

The square root of 640672667 is about 25311.5125387639. The cubic root of 640672667 is about 862.0756905308.

The spelling of 640672667 in words is "six hundred forty million, six hundred seventy-two thousand, six hundred sixty-seven".