20806778 has 4 divisors (see below), whose sum is σ = 31210170. Its totient is φ = 10403388.

The previous prime is 20806777. The next prime is 20806801. The reversal of 20806778 is 87760802.

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., 13227769 + 7579009 = 3637^2 + 2753^2 .

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20806777) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5201693 + ... + 5201696.

Almost surely, 2^20806778 is an apocalyptic number.

20806778 is a deficient number, since it is larger than the sum of its proper divisors (10403392).

20806778 is a wasteful number, since it uses less digits than its factorization.

20806778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10403391.

The product of its (nonzero) digits is 37632, while the sum is 38.

The square root of 20806778 is about 4561.4447272767. Note that the first 3 decimals coincide. The cubic root of 20806778 is about 275.0436426603.

The spelling of 20806778 in words is "twenty million, eight hundred six thousand, seven hundred seventy-eight".