647199991 has 2 divisors, whose sum is σ = 647199992. Its totient is φ = 647199990.

The previous prime is 647199977. The next prime is 647200033. The reversal of 647199991 is 199991746.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 647199991 - 2²⁵ = 613645559 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (647199491) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323599995 + 323599996.

It is an arithmetic number, because the mean of its divisors is an integer number (323599996).

Almost surely, 2^647199991 is an apocalyptic number.

647199991 is a deficient number, since it is larger than the sum of its proper divisors (1).

647199991 is an equidigital number, since it uses as much as digits as its factorization.

647199991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1102248, while the sum is 55.

The square root of 647199991 is about 25440.1256089666. The cubic root of 647199991 is about 864.9934805215.

The spelling of 647199991 in words is "six hundred forty-seven million, one hundred ninety-nine thousand, nine hundred ninety-one".