91000000981 has 2 divisors, whose sum is σ = 91000000982. Its totient is φ = 91000000980.

The previous prime is 91000000957. The next prime is 91000000991. The reversal of 91000000981 is 18900000019.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 70548140881 + 20451860100 = 265609^2 + 143010^2 .

It is a cyclic number.

It is not a de Polignac number, because 91000000981 - 2¹¹ = 90999998933 is a prime.

It is a super-2 number, since 2×91000000981² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91000000921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45500000490 + 45500000491.

It is an arithmetic number, because the mean of its divisors is an integer number (45500000491).

Almost surely, 2^91000000981 is an apocalyptic number.

It is an amenable number.

91000000981 is a deficient number, since it is larger than the sum of its proper divisors (1).

91000000981 is an equidigital number, since it uses as much as digits as its factorization.

91000000981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 648, while the sum is 28.

The spelling of 91000000981 in words is "ninety-one billion, nine hundred eighty-one", and thus it is an aban number.