20918911 has 4 divisors (see below), whose sum is σ = 22528072. Its totient is φ = 19309752.

The previous prime is 20918851. The next prime is 20918917. The reversal of 20918911 is 11981902.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20918911 - 2⁷ = 20918783 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 (20918917) 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, 804561 + ... + 804586.

It is an arithmetic number, because the mean of its divisors is an integer number (5632018).

Almost surely, 2^20918911 is an apocalyptic number.

20918911 is a deficient number, since it is larger than the sum of its proper divisors (1609161).

20918911 is a wasteful number, since it uses less digits than its factorization.

20918911 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1609160.

The product of its (nonzero) digits is 1296, while the sum is 31.

The square root of 20918911 is about 4573.7196022494. The cubic root of 20918911 is about 275.5368510098.

The spelling of 20918911 in words is "twenty million, nine hundred eighteen thousand, nine hundred eleven".