21561606834 has 16 divisors (see below), whose sum is σ = 43139259072. Its totient is φ = 7184528048.

The previous prime is 21561606827. The next prime is 21561606839. The reversal of 21561606834 is 43860616512.

It is not an unprimeable number, because it can be changed into a prime (21561606839) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 651054 + ... + 683369.

It is an arithmetic number, because the mean of its divisors is an integer number (2696203692).

Almost surely, 2^21561606834 is an apocalyptic number.

21561606834 is an abundant number, since it is smaller than the sum of its proper divisors (21577652238).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21561606834 is a wasteful number, since it uses less digits than its factorization.

21561606834 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1337121.

The product of its (nonzero) digits is 207360, while the sum is 42.

The spelling of 21561606834 in words is "twenty-one billion, five hundred sixty-one million, six hundred six thousand, eight hundred thirty-four".