21561816067 has 12 divisors (see below), whose sum is σ = 23832605160. Its totient is φ = 19492124960.

The previous prime is 21561815969. The next prime is 21561816077. The reversal of 21561816067 is 76061816512.

It is not a de Polignac number, because 21561816067 - 2⁷ = 21561815939 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21561816077) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 476098 + ... + 519415.

It is an arithmetic number, because the mean of its divisors is an integer number (1986050430).

Almost surely, 2^21561816067 is an apocalyptic number.

21561816067 is a deficient number, since it is larger than the sum of its proper divisors (2270789093).

21561816067 is a wasteful number, since it uses less digits than its factorization.

21561816067 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 995714 (or 995703 counting only the distinct ones).

The product of its (nonzero) digits is 120960, while the sum is 43.

The spelling of 21561816067 in words is "twenty-one billion, five hundred sixty-one million, eight hundred sixteen thousand, sixty-seven".