20787917 has 2 divisors, whose sum is σ = 20787918. Its totient is φ = 20787916.

The previous prime is 20787913. The next prime is 20787941. The reversal of 20787917 is 71978702.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20666116 + 121801 = 4546^2 + 349^2 .

It is a cyclic number.

It is not a de Polignac number, because 20787917 - 2² = 20787913 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20787911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10393958 + 10393959.

It is an arithmetic number, because the mean of its divisors is an integer number (10393959).

Almost surely, 2^20787917 is an apocalyptic number.

It is an amenable number.

20787917 is a deficient number, since it is larger than the sum of its proper divisors (1).

20787917 is an equidigital number, since it uses as much as digits as its factorization.

20787917 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 49392, while the sum is 41.

The square root of 20787917 is about 4559.3768214527. The cubic root of 20787917 is about 274.9605100320.

The spelling of 20787917 in words is "twenty million, seven hundred eighty-seven thousand, nine hundred seventeen".