20918945 has 4 divisors (see below), whose sum is σ = 25102740. Its totient is φ = 16735152.

The previous prime is 20918939. The next prime is 20918951. The reversal of 20918945 is 54981902.

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

It is an interprime number because it is at equal distance from previous prime (20918939) and next prime (20918951).

It can be written as a sum of positive squares in 2 ways, for example, as 16386304 + 4532641 = 4048^2 + 2129^2 .

It is a cyclic number.

It is not a de Polignac number, because 20918945 - 2⁴ = 20918929 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20918899 and 20918908.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 2091890 + ... + 2091899.

It is an arithmetic number, because the mean of its divisors is an integer number (6275685).

Almost surely, 2^20918945 is an apocalyptic number.

It is an amenable number.

20918945 is a deficient number, since it is larger than the sum of its proper divisors (4183795).

20918945 is an equidigital number, since it uses as much as digits as its factorization.

20918945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4183794.

The product of its (nonzero) digits is 25920, while the sum is 38.

The square root of 20918945 is about 4573.7233191351. The cubic root of 20918945 is about 275.5370002886.

The spelling of 20918945 in words is "twenty million, nine hundred eighteen thousand, nine hundred forty-five".