636902451616561 has 4 divisors (see below), whose sum is σ = 685894947894772. Its totient is φ = 587909955338352.

The previous prime is 636902451616531. The next prime is 636902451616567. The reversal of 636902451616561 is 165616154209636.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 295797345537600 + 341105106078961 = 17198760^2 + 18469031^2 .

It is a cyclic number.

It is not a de Polignac number, because 636902451616561 - 2³⁹ = 636352695802673 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 636902451616561.

It is not an unprimeable number, because it can be changed into a prime (636902451616567) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24496248139086 + ... + 24496248139111.

It is an arithmetic number, because the mean of its divisors is an integer number (171473736973693).

Almost surely, 2^{636902451616561} is an apocalyptic number.

It is an amenable number.

636902451616561 is a deficient number, since it is larger than the sum of its proper divisors (48992496278211).

636902451616561 is a wasteful number, since it uses less digits than its factorization.

636902451616561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48992496278210.

The product of its (nonzero) digits is 41990400, while the sum is 61.

The spelling of 636902451616561 in words is "six hundred thirty-six trillion, nine hundred two billion, four hundred fifty-one million, six hundred sixteen thousand, five hundred sixty-one".