9997827781 has 2 divisors, whose sum is σ = 9997827782. Its totient is φ = 9997827780.

The previous prime is 9997827769. The next prime is 9997827811. The reversal of 9997827781 is 1877287999.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 5676869025 + 4320958756 = 75345^2 + 65734^2 .

It is a cyclic number.

It is not a de Polignac number, because 9997827781 - 2⁹ = 9997827269 is a prime.

It is a super-2 number, since 2×9997827781² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9997827751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4998913890 + 4998913891.

It is an arithmetic number, because the mean of its divisors is an integer number (4998913891).

Almost surely, 2^9997827781 is an apocalyptic number.

It is an amenable number.

9997827781 is a deficient number, since it is larger than the sum of its proper divisors (1).

9997827781 is an equidigital number, since it uses as much as digits as its factorization.

9997827781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 32006016, while the sum is 67.

The square root of 9997827781 is about 99989.1383151190. The cubic root of 9997827781 is about 2154.2786819363.

The spelling of 9997827781 in words is "nine billion, nine hundred ninety-seven million, eight hundred twenty-seven thousand, seven hundred eighty-one".