20778881 has 2 divisors, whose sum is σ = 20778882. Its totient is φ = 20778880.

The previous prime is 20778871. The next prime is 20778883. The reversal of 20778881 is 18887702.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20611600 + 167281 = 4540^2 + 409^2 .

It is a cyclic number.

It is not a de Polignac number, because 20778881 - 2¹⁸ = 20516737 is a prime.

It is a super-2 number, since 2×20778881² = 863523791224322, which contains 22 as substring.

Together with 20778883, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20778883) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10389440 + 10389441.

It is an arithmetic number, because the mean of its divisors is an integer number (10389441).

Almost surely, 2^20778881 is an apocalyptic number.

It is an amenable number.

20778881 is a deficient number, since it is larger than the sum of its proper divisors (1).

20778881 is an equidigital number, since it uses as much as digits as its factorization.

20778881 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 50176, while the sum is 41.

The square root of 20778881 is about 4558.3857888511. The cubic root of 20778881 is about 274.9206647179.

The spelling of 20778881 in words is "twenty million, seven hundred seventy-eight thousand, eight hundred eighty-one".