9215999981 has 2 divisors, whose sum is σ = 9215999982. Its totient is φ = 9215999980.

The previous prime is 9215999971. The next prime is 9216000011. The reversal of 9215999981 is 1899995129.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 5792579881 + 3423420100 = 76109^2 + 58510^2 .

It is an emirp because it is prime and its reverse (1899995129) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 9215999981 - 2⁶ = 9215999917 is a prime.

It is a super-2 number, since 2×9215999981² (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 (9215999971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4607999990 + 4607999991.

It is an arithmetic number, because the mean of its divisors is an integer number (4607999991).

Almost surely, 2^9215999981 is an apocalyptic number.

It is an amenable number.

9215999981 is a deficient number, since it is larger than the sum of its proper divisors (1).

9215999981 is an equidigital number, since it uses as much as digits as its factorization.

9215999981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4723920, while the sum is 62.

The square root of 9215999981 is about 95999.9999010417. Note that the first 4 decimals coincide. The cubic root of 9215999981 is about 2096.5931139263.

The spelling of 9215999981 in words is "nine billion, two hundred fifteen million, nine hundred ninety-nine thousand, nine hundred eighty-one".