636945661 has 4 divisors (see below), whose sum is σ = 694849824. Its totient is φ = 579041500.

The previous prime is 636945649. The next prime is 636945671. The reversal of 636945661 is 166549636.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 636945661 - 2⁵ = 636945629 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (636945611) 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, 28952065 + ... + 28952086.

It is an arithmetic number, because the mean of its divisors is an integer number (173712456).

Almost surely, 2^636945661 is an apocalyptic number.

It is an amenable number.

636945661 is a deficient number, since it is larger than the sum of its proper divisors (57904163).

636945661 is a wasteful number, since it uses less digits than its factorization.

636945661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57904162.

The product of its digits is 699840, while the sum is 46.

The square root of 636945661 is about 25237.7824105051. The cubic root of 636945661 is about 860.4007781359.

The spelling of 636945661 in words is "six hundred thirty-six million, nine hundred forty-five thousand, six hundred sixty-one".