91010101981 has 2 divisors, whose sum is σ = 91010101982. Its totient is φ = 91010101980.

The previous prime is 91010101951. The next prime is 91010102017. The reversal of 91010101981 is 18910101019.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 90045005625 + 965096356 = 300075^2 + 31066^2 .

It is an emirp because it is prime and its reverse (18910101019) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 91010101981 - 2³⁵ = 56650363613 is a prime.

It is a super-2 number, since 2×91010101981² (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 (91010101951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45505050990 + 45505050991.

It is an arithmetic number, because the mean of its divisors is an integer number (45505050991).

Almost surely, 2^91010101981 is an apocalyptic number.

It is an amenable number.

91010101981 is a deficient number, since it is larger than the sum of its proper divisors (1).

91010101981 is an equidigital number, since it uses as much as digits as its factorization.

91010101981 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 31.

The spelling of 91010101981 in words is "ninety-one billion, ten million, one hundred one thousand, nine hundred eighty-one".