91007821 has 4 divisors (see below), whose sum is σ = 91029600. Its totient is φ = 90986044.

The previous prime is 91007797. The next prime is 91007843. The reversal of 91007821 is 12870019.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12870019 = 2927 ⋅4397.

It is a cyclic number.

It is not a de Polignac number, because 91007821 - 2⁵ = 91007789 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 91007821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91007881) 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, 2431 + ... + 13708.

It is an arithmetic number, because the mean of its divisors is an integer number (22757400).

Almost surely, 2^91007821 is an apocalyptic number.

It is an amenable number.

91007821 is a deficient number, since it is larger than the sum of its proper divisors (21779).

91007821 is a wasteful number, since it uses less digits than its factorization.

91007821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21778.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 91007821 is about 9539.8019371473. The cubic root of 91007821 is about 449.8070300192.

The spelling of 91007821 in words is "ninety-one million, seven thousand, eight hundred twenty-one".