91290821 has 4 divisors (see below), whose sum is σ = 91367052. Its totient is φ = 91214592.

The previous prime is 91290791. The next prime is 91290851. The reversal of 91290821 is 12809219.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12809219 = 1409 ⋅9091.

It is an interprime number because it is at equal distance from previous prime (91290791) and next prime (91290851).

It can be written as a sum of positive squares in 2 ways, for example, as 65788321 + 25502500 = 8111^2 + 5050^2 .

It is a cyclic number.

It is not a de Polignac number, because 91290821 - 2⁶ = 91290757 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91290851) 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, 36290 + ... + 38723.

It is an arithmetic number, because the mean of its divisors is an integer number (22841763).

Almost surely, 2^91290821 is an apocalyptic number.

It is an amenable number.

91290821 is a deficient number, since it is larger than the sum of its proper divisors (76231).

91290821 is a wasteful number, since it uses less digits than its factorization.

91290821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 76230.

The product of its (nonzero) digits is 2592, while the sum is 32.

The square root of 91290821 is about 9554.6230171577. The cubic root of 91290821 is about 450.2727909787.

The spelling of 91290821 in words is "ninety-one million, two hundred ninety thousand, eight hundred twenty-one".