9891521797 has 2 divisors, whose sum is σ = 9891521798. Its totient is φ = 9891521796.

The previous prime is 9891521741. The next prime is 9891521807. The reversal of 9891521797 is 7971251989.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9761242401 + 130279396 = 98799^2 + 11414^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9891521797 is a prime.

It is a super-2 number, since 2×9891521797² (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 (9891521737) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4945760898 + 4945760899.

It is an arithmetic number, because the mean of its divisors is an integer number (4945760899).

Almost surely, 2^9891521797 is an apocalyptic number.

It is an amenable number.

9891521797 is a deficient number, since it is larger than the sum of its proper divisors (1).

9891521797 is an equidigital number, since it uses as much as digits as its factorization.

9891521797 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2857680, while the sum is 58.

The square root of 9891521797 is about 99456.1300121818. The cubic root of 9891521797 is about 2146.6160429590.

The spelling of 9891521797 in words is "nine billion, eight hundred ninety-one million, five hundred twenty-one thousand, seven hundred ninety-seven".