20317981 has 2 divisors, whose sum is σ = 20317982. Its totient is φ = 20317980.

The previous prime is 20317967. The next prime is 20317991. The reversal of 20317981 is 18971302.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15327225 + 4990756 = 3915^2 + 2234^2 .

It is a cyclic number.

It is not a de Polignac number, because 20317981 - 2⁵ = 20317949 is a prime.

It is a super-2 number, since 2×20317981² = 825640703832722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20317991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10158990 + 10158991.

It is an arithmetic number, because the mean of its divisors is an integer number (10158991).

Almost surely, 2^20317981 is an apocalyptic number.

It is an amenable number.

20317981 is a deficient number, since it is larger than the sum of its proper divisors (1).

20317981 is an equidigital number, since it uses as much as digits as its factorization.

20317981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 20317981 is about 4507.5471156717. The cubic root of 20317981 is about 272.8727597865.

The spelling of 20317981 in words is "twenty million, three hundred seventeen thousand, nine hundred eighty-one".