91021013 has 2 divisors, whose sum is σ = 91021014. Its totient is φ = 91021012.

The previous prime is 91020989. The next prime is 91021031. The reversal of 91021013 is 31012019.

It is a happy number.

Together with next prime (91021031) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 57866449 + 33154564 = 7607^2 + 5758^2 .

It is a cyclic number.

It is not a de Polignac number, because 91021013 - 2⁶ = 91020949 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 91020982 and 91021000.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91021033) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45510506 + 45510507.

It is an arithmetic number, because the mean of its divisors is an integer number (45510507).

Almost surely, 2^91021013 is an apocalyptic number.

It is an amenable number.

91021013 is a deficient number, since it is larger than the sum of its proper divisors (1).

91021013 is an equidigital number, since it uses as much as digits as its factorization.

91021013 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 54, while the sum is 17.

The square root of 91021013 is about 9540.4933310600. The cubic root of 91021013 is about 449.8287628314.

The spelling of 91021013 in words is "ninety-one million, twenty-one thousand, thirteen".