21205530672 has 20 divisors (see below), whose sum is σ = 54780954360. Its totient is φ = 7068510208.

The previous prime is 21205530653. The next prime is 21205530719. The reversal of 21205530672 is 27603550212.

It is a super-2 number, since 2×21205530672² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 220890897 + ... + 220890992.

It is an arithmetic number, because the mean of its divisors is an integer number (2739047718).

Almost surely, 2^21205530672 is an apocalyptic number.

It is an amenable number.

21205530672 is an abundant number, since it is smaller than the sum of its proper divisors (33575423688).

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

21205530672 is a wasteful number, since it uses less digits than its factorization.

21205530672 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 441781900 (or 441781894 counting only the distinct ones).

The product of its (nonzero) digits is 25200, while the sum is 33.

The spelling of 21205530672 in words is "twenty-one billion, two hundred five million, five hundred thirty thousand, six hundred seventy-two".