636402121 has 2 divisors, whose sum is σ = 636402122. Its totient is φ = 636402120.

The previous prime is 636402119. The next prime is 636402163. The reversal of 636402121 is 121204636.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 460574521 + 175827600 = 21461^2 + 13260^2 .

It is a cyclic number.

It is not a de Polignac number, because 636402121 - 2¹ = 636402119 is a prime.

It is a super-2 number, since 2×636402121² = 810015319226597282, which contains 22 as substring.

Together with 636402119, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (636402521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 318201060 + 318201061.

It is an arithmetic number, because the mean of its divisors is an integer number (318201061).

Almost surely, 2^636402121 is an apocalyptic number.

It is an amenable number.

636402121 is a deficient number, since it is larger than the sum of its proper divisors (1).

636402121 is an equidigital number, since it uses as much as digits as its factorization.

636402121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1728, while the sum is 25.

The square root of 636402121 is about 25227.0117334575. The cubic root of 636402121 is about 860.1559663946.

Adding to 636402121 its reverse (121204636), we get a palindrome (757606757).

The spelling of 636402121 in words is "six hundred thirty-six million, four hundred two thousand, one hundred twenty-one".