647663561 has 2 divisors, whose sum is σ = 647663562. Its totient is φ = 647663560.

The previous prime is 647663543. The next prime is 647663579. The reversal of 647663561 is 165366746.

It is a balanced prime because it is at equal distance from previous prime (647663543) and next prime (647663579).

It can be written as a sum of positive squares in only one way, i.e., 354192400 + 293471161 = 18820^2 + 17131^2 .

It is a cyclic number.

It is not a de Polignac number, because 647663561 - 2¹⁰ = 647662537 is a prime.

It is not a weakly prime, because it can be changed into another prime (647663761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323831780 + 323831781.

It is an arithmetic number, because the mean of its divisors is an integer number (323831781).

Almost surely, 2^647663561 is an apocalyptic number.

It is an amenable number.

647663561 is a deficient number, since it is larger than the sum of its proper divisors (1).

647663561 is an equidigital number, since it uses as much as digits as its factorization.

647663561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 544320, while the sum is 44.

The square root of 647663561 is about 25449.2349786786. The cubic root of 647663561 is about 865.1999542203.

The spelling of 647663561 in words is "six hundred forty-seven million, six hundred sixty-three thousand, five hundred sixty-one".