9997640561 has 2 divisors, whose sum is σ = 9997640562. Its totient is φ = 9997640560.

The previous prime is 9997640539. The next prime is 9997640563. The reversal of 9997640561 is 1650467999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9794862961 + 202777600 = 98969^2 + 14240^2 .

It is an emirp because it is prime and its reverse (1650467999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 9997640561 - 2¹⁰ = 9997639537 is a prime.

Together with 9997640563, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 9997640497 and 9997640506.

It is not a weakly prime, because it can be changed into another prime (9997640563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4998820280 + 4998820281.

It is an arithmetic number, because the mean of its divisors is an integer number (4998820281).

Almost surely, 2^9997640561 is an apocalyptic number.

It is an amenable number.

9997640561 is a deficient number, since it is larger than the sum of its proper divisors (1).

9997640561 is an equidigital number, since it uses as much as digits as its factorization.

9997640561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3674160, while the sum is 56.

The square root of 9997640561 is about 99988.2021090488. The cubic root of 9997640561 is about 2154.2652347962.

The spelling of 9997640561 in words is "nine billion, nine hundred ninety-seven million, six hundred forty thousand, five hundred sixty-one".