20786681 has 2 divisors, whose sum is σ = 20786682. Its totient is φ = 20786680.

The previous prime is 20786669. The next prime is 20786719. The reversal of 20786681 is 18668702.

It is an a-pointer prime, because the next prime (20786719) can be obtained adding 20786681 to its sum of digits (38).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13388281 + 7398400 = 3659^2 + 2720^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20786681 is a prime.

It is a super-2 number, since 2×20786681² = 864172213991522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20786611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10393340 + 10393341.

It is an arithmetic number, because the mean of its divisors is an integer number (10393341).

Almost surely, 2^20786681 is an apocalyptic number.

It is an amenable number.

20786681 is a deficient number, since it is larger than the sum of its proper divisors (1).

20786681 is an equidigital number, since it uses as much as digits as its factorization.

20786681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32256, while the sum is 38.

The square root of 20786681 is about 4559.2412745982. The cubic root of 20786681 is about 274.9550604251.

The spelling of 20786681 in words is "twenty million, seven hundred eighty-six thousand, six hundred eighty-one".