636638081 has 2 divisors, whose sum is σ = 636638082. Its totient is φ = 636638080.

The previous prime is 636638069. The next prime is 636638089. The reversal of 636638081 is 180836636.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 382554481 + 254083600 = 19559^2 + 15940^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-636638081 is a prime.

It is a super-2 number, since 2×636638081² = 810616092358725122, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (636638089) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 318319040 + 318319041.

It is an arithmetic number, because the mean of its divisors is an integer number (318319041).

Almost surely, 2^636638081 is an apocalyptic number.

It is an amenable number.

636638081 is a deficient number, since it is larger than the sum of its proper divisors (1).

636638081 is an equidigital number, since it uses as much as digits as its factorization.

636638081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 124416, while the sum is 41.

The square root of 636638081 is about 25231.6880331063. The cubic root of 636638081 is about 860.2622604688.

The spelling of 636638081 in words is "six hundred thirty-six million, six hundred thirty-eight thousand, eighty-one".