21106591 has 8 divisors (see below), whose sum is σ = 23154768. Its totient is φ = 19080000.

The previous prime is 21106583. The next prime is 21106607. The reversal of 21106591 is 19560112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21106591 - 2³ = 21106583 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 (21106531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3310 + ... + 7291.

It is an arithmetic number, because the mean of its divisors is an integer number (2894346).

Almost surely, 2^21106591 is an apocalyptic number.

21106591 is a deficient number, since it is larger than the sum of its proper divisors (2048177).

21106591 is a wasteful number, since it uses less digits than its factorization.

21106591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10793.

The product of its (nonzero) digits is 540, while the sum is 25.

The square root of 21106591 is about 4594.1910060423. The cubic root of 21106591 is about 276.3584181637.

The spelling of 21106591 in words is "twenty-one million, one hundred six thousand, five hundred ninety-one".