9891415921 has 2 divisors, whose sum is σ = 9891415922. Its totient is φ = 9891415920.

The previous prime is 9891415909. The next prime is 9891415931. The reversal of 9891415921 is 1295141989.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7523133696 + 2368282225 = 86736^2 + 48665^2 .

It is a cyclic number.

It is not a de Polignac number, because 9891415921 - 2⁵ = 9891415889 is a prime.

It is a super-3 number, since 3×9891415921³ (a number of 31 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (9891415931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4945707960 + 4945707961.

It is an arithmetic number, because the mean of its divisors is an integer number (4945707961).

Almost surely, 2^9891415921 is an apocalyptic number.

It is an amenable number.

9891415921 is a deficient number, since it is larger than the sum of its proper divisors (1).

9891415921 is an equidigital number, since it uses as much as digits as its factorization.

9891415921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 233280, while the sum is 49.

The square root of 9891415921 is about 99455.5977358741. The cubic root of 9891415921 is about 2146.6083840118.

The spelling of 9891415921 in words is "nine billion, eight hundred ninety-one million, four hundred fifteen thousand, nine hundred twenty-one".