91021 has 4 divisors (see below), whose sum is σ = 104032. Its totient is φ = 78012.

The previous prime is 91019. The next prime is 91033. The reversal of 91021 is 12019.

91021 is nontrivially palindromic in base 2.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 91021 - 2¹ = 91019 is a prime.

It is a Duffinian number.

91021 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 90992 and 91010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91081) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6495 + ... + 6508.

It is an arithmetic number, because the mean of its divisors is an integer number (26008).

2⁹¹⁰²¹ is an apocalyptic number.

It is an amenable number.

91021 is a deficient number, since it is larger than the sum of its proper divisors (13011).

91021 is a wasteful number, since it uses less digits than its factorization.

91021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13010.

The product of its (nonzero) digits is 18, while the sum is 13.

The square root of 91021 is about 301.6968677332. The cubic root of 91021 is about 44.9828741416.

It can be divided in two parts, 910 and 21, that multiplied together give a triangular number (19110 = T₁₉₅).

The spelling of 91021 in words is "ninety-one thousand, twenty-one".