636789636081 has 27 divisors (see below), whose sum is σ = 923407177953. Its totient is φ = 422871390720.

The previous prime is 636789636071. The next prime is 636789636083. The reversal of 636789636081 is 180636987636.

The square root of 636789636081 is 797991.

It is a perfect power (a square), and thus also a powerful number.

636789636081 is a `hidden beast` number, since 6 + 367 + 89 + 63 + 60 + 81 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 156424205025 + 480365431056 = 395505^2 + 693084^2 .

It is not a de Polignac number, because 636789636081 - 2²⁷ = 636655418353 is a prime.

It is a super-2 number, since 2×636789636081² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (636789636083) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 1103621265 + ... + 1103621841.

Almost surely, 2^636789636081 is an apocalyptic number.

636789636081 is the 797991-st square number.

636789636081 is the 398996-th centered octagonal number.

It is an amenable number.

636789636081 is a deficient number, since it is larger than the sum of its proper divisors (286617541872).

636789636081 is an frugal number, since it uses more digits than its factorization.

636789636081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2082 (or 1041 counting only the distinct ones).

The product of its (nonzero) digits is 47029248, while the sum is 63.

The spelling of 636789636081 in words is "six hundred thirty-six billion, seven hundred eighty-nine million, six hundred thirty-six thousand, eighty-one".