647644691 has 2 divisors, whose sum is σ = 647644692. Its totient is φ = 647644690.

The previous prime is 647644687. The next prime is 647644709. The reversal of 647644691 is 196446746.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 647644691 - 2² = 647644687 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (647644091) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323822345 + 323822346.

It is an arithmetic number, because the mean of its divisors is an integer number (323822346).

Almost surely, 2^647644691 is an apocalyptic number.

647644691 is a deficient number, since it is larger than the sum of its proper divisors (1).

647644691 is an equidigital number, since it uses as much as digits as its factorization.

647644691 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 870912, while the sum is 47.

The square root of 647644691 is about 25448.8642379184. The cubic root of 647644691 is about 865.1915514617.

The spelling of 647644691 in words is "six hundred forty-seven million, six hundred forty-four thousand, six hundred ninety-one".