20956591 has 4 divisors (see below), whose sum is σ = 21164184. Its totient is φ = 20749000.

The previous prime is 20956583. The next prime is 20956627. The reversal of 20956591 is 19565902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19565902 = 2 ⋅9782951.

It is a cyclic number.

It is not a de Polignac number, because 20956591 - 2³ = 20956583 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 20956591.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20956511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 103645 + ... + 103846.

It is an arithmetic number, because the mean of its divisors is an integer number (5291046).

Almost surely, 2^20956591 is an apocalyptic number.

20956591 is a deficient number, since it is larger than the sum of its proper divisors (207593).

20956591 is a wasteful number, since it uses less digits than its factorization.

20956591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 207592.

The product of its (nonzero) digits is 24300, while the sum is 37.

The square root of 20956591 is about 4577.8369346232. The cubic root of 20956591 is about 275.7021878692.

The spelling of 20956591 in words is "twenty million, nine hundred fifty-six thousand, five hundred ninety-one".