21091093 has 4 divisors (see below), whose sum is σ = 21100480. Its totient is φ = 21081708.

The previous prime is 21091079. The next prime is 21091139. The reversal of 21091093 is 39019012.

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 a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21091093 - 2²¹ = 18993941 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 (21091003) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 898 + ... + 6556.

It is an arithmetic number, because the mean of its divisors is an integer number (5275120).

Almost surely, 2^21091093 is an apocalyptic number.

It is an amenable number.

21091093 is a deficient number, since it is larger than the sum of its proper divisors (9387).

21091093 is an equidigital number, since it uses as much as digits as its factorization.

21091093 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9386.

The product of its (nonzero) digits is 486, while the sum is 25.

The square root of 21091093 is about 4592.5040010870. The cubic root of 21091093 is about 276.2907607593.

The spelling of 21091093 in words is "twenty-one million, ninety-one thousand, ninety-three".