20906978 has 8 divisors (see below), whose sum is σ = 31413468. Its totient is φ = 10435824.

The previous prime is 20906971. The next prime is 20907001. The reversal of 20906978 is 87960902.

It can be written as a sum of positive squares in 2 ways, for example, as 17247409 + 3659569 = 4153^2 + 1913^2 .

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

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20906971) 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 3 ways as a sum of consecutive naturals, for example, 7301 + ... + 9752.

Almost surely, 2^20906978 is an apocalyptic number.

20906978 is a deficient number, since it is larger than the sum of its proper divisors (10506490).

20906978 is a wasteful number, since it uses less digits than its factorization.

20906978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17668.

The product of its (nonzero) digits is 54432, while the sum is 41.

The square root of 20906978 is about 4572.4148980599. The cubic root of 20906978 is about 275.4844485585.

The spelling of 20906978 in words is "twenty million, nine hundred six thousand, nine hundred seventy-eight".