21216361566 has 32 divisors (see below), whose sum is σ = 43183048608. Its totient is φ = 6947360640.

The previous prime is 21216361559. The next prime is 21216361597. The reversal of 21216361566 is 66516361212.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 255336 + ... + 328068.

It is an arithmetic number, because the mean of its divisors is an integer number (1349470269).

Almost surely, 2^21216361566 is an apocalyptic number.

21216361566 is an abundant number, since it is smaller than the sum of its proper divisors (21966687042).

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

21216361566 is a wasteful number, since it uses less digits than its factorization.

21216361566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73596.

The product of its digits is 77760, while the sum is 39.

The spelling of 21216361566 in words is "twenty-one billion, two hundred sixteen million, three hundred sixty-one thousand, five hundred sixty-six".