20905778 has 4 divisors (see below), whose sum is σ = 31358670. Its totient is φ = 10452888.

The previous prime is 20905771. The next prime is 20905817. The reversal of 20905778 is 87750902.

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

It can be written as a sum of positive squares in only one way, i.e., 19775809 + 1129969 = 4447^2 + 1063^2 .

It is not an unprimeable number, because it can be changed into a prime (20905771) 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 as a sum of consecutive naturals, namely, 5226443 + ... + 5226446.

Almost surely, 2^20905778 is an apocalyptic number.

20905778 is a deficient number, since it is larger than the sum of its proper divisors (10452892).

20905778 is a wasteful number, since it uses less digits than its factorization.

20905778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10452891.

The product of its (nonzero) digits is 35280, while the sum is 38.

The square root of 20905778 is about 4572.2836744891. The cubic root of 20905778 is about 275.4791777878.

The spelling of 20905778 in words is "twenty million, nine hundred five thousand, seven hundred seventy-eight".