21461665566 has 16 divisors (see below), whose sum is σ = 46825452288. Its totient is φ = 6503535000.

The previous prime is 21461665559. The next prime is 21461665571. The reversal of 21461665566 is 66556616412.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 162588310 + ... + 162588441.

It is an arithmetic number, because the mean of its divisors is an integer number (2926590768).

Almost surely, 2^21461665566 is an apocalyptic number.

21461665566 is an abundant number, since it is smaller than the sum of its proper divisors (25363786722).

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

21461665566 is a wasteful number, since it uses less digits than its factorization.

21461665566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 325176767.

The product of its digits is 1555200, while the sum is 48.

The spelling of 21461665566 in words is "twenty-one billion, four hundred sixty-one million, six hundred sixty-five thousand, five hundred sixty-six".