100636561 has 4 divisors (see below), whose sum is σ = 100869412. Its totient is φ = 100403712.

The previous prime is 100636499. The next prime is 100636567. The reversal of 100636561 is 165636001.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 165636001 = 2333 ⋅70997.

It can be written as a sum of positive squares in 2 ways, for example, as 22420225 + 78216336 = 4735^2 + 8844^2 .

It is a cyclic number.

It is not a de Polignac number, because 100636561 - 2⁹ = 100636049 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (100636567) 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, 115776 + ... + 116641.

It is an arithmetic number, because the mean of its divisors is an integer number (25217353).

Almost surely, 2^100636561 is an apocalyptic number.

It is an amenable number.

100636561 is a deficient number, since it is larger than the sum of its proper divisors (232851).

100636561 is an equidigital number, since it uses as much as digits as its factorization.

100636561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 232850.

The product of its (nonzero) digits is 3240, while the sum is 28.

The square root of 100636561 is about 10031.7775593361. Note that the first 3 decimals coincide. The cubic root of 100636561 is about 465.1416857328.

The spelling of 100636561 in words is "one hundred million, six hundred thirty-six thousand, five hundred sixty-one".