636657121 has 2 divisors, whose sum is σ = 636657122. Its totient is φ = 636657120.

The previous prime is 636657103. The next prime is 636657247. The reversal of 636657121 is 121756636.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 550371600 + 86285521 = 23460^2 + 9289^2 .

It is a cyclic number.

It is not a de Polignac number, because 636657121 - 2⁹ = 636656609 is a prime.

It is not a weakly prime, because it can be changed into another prime (636657101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 318328560 + 318328561.

It is an arithmetic number, because the mean of its divisors is an integer number (318328561).

Almost surely, 2^636657121 is an apocalyptic number.

It is an amenable number.

636657121 is a deficient number, since it is larger than the sum of its proper divisors (1).

636657121 is an equidigital number, since it uses as much as digits as its factorization.

636657121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 45360, while the sum is 37.

The square root of 636657121 is about 25232.0653336186. The cubic root of 636657121 is about 860.2708363670.

The spelling of 636657121 in words is "six hundred thirty-six million, six hundred fifty-seven thousand, one hundred twenty-one".