63561909891 has 4 divisors (see below), whose sum is σ = 84749213192. Its totient is φ = 42374606592.

The previous prime is 63561909881. The next prime is 63561909937. The reversal of 63561909891 is 19890916536.

63561909891 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is not a de Polignac number, because 63561909891 - 2⁹ = 63561909379 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (63561909811) 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, 10593651646 + ... + 10593651651.

It is an arithmetic number, because the mean of its divisors is an integer number (21187303298).

Almost surely, 2^63561909891 is an apocalyptic number.

63561909891 is a deficient number, since it is larger than the sum of its proper divisors (21187303301).

63561909891 is a wasteful number, since it uses less digits than its factorization.

63561909891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21187303300.

The product of its (nonzero) digits is 3149280, while the sum is 57.

The spelling of 63561909891 in words is "sixty-three billion, five hundred sixty-one million, nine hundred nine thousand, eight hundred ninety-one".