20717251 has 2 divisors, whose sum is σ = 20717252. Its totient is φ = 20717250.

The previous prime is 20717231. The next prime is 20717261. The reversal of 20717251 is 15271702.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20717251 - 2⁵ = 20717219 is a prime.

It is not a weakly prime, because it can be changed into another prime (20717231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10358625 + 10358626.

It is an arithmetic number, because the mean of its divisors is an integer number (10358626).

Almost surely, 2^20717251 is an apocalyptic number.

20717251 is a deficient number, since it is larger than the sum of its proper divisors (1).

20717251 is an equidigital number, since it uses as much as digits as its factorization.

20717251 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 980, while the sum is 25.

The square root of 20717251 is about 4551.6207003660. The cubic root of 20717251 is about 274.6485913643.

Adding to 20717251 its reverse (15271702), we get a palindrome (35988953).

The spelling of 20717251 in words is "twenty million, seven hundred seventeen thousand, two hundred fifty-one".