20907778 has 4 divisors (see below), whose sum is σ = 31361670. Its totient is φ = 10453888.

The previous prime is 20907767. The next prime is 20907781. The reversal of 20907778 is 87770902.

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., 10712529 + 10195249 = 3273^2 + 3193^2 .

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 20907778.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5226943 + ... + 5226946.

Almost surely, 2^20907778 is an apocalyptic number.

20907778 is a deficient number, since it is larger than the sum of its proper divisors (10453892).

20907778 is a wasteful number, since it uses less digits than its factorization.

20907778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10453891.

The product of its (nonzero) digits is 49392, while the sum is 40.

The square root of 20907778 is about 4572.5023783482. The cubic root of 20907778 is about 275.4879622937.

The spelling of 20907778 in words is "twenty million, nine hundred seven thousand, seven hundred seventy-eight".