21205605712 has 20 divisors (see below), whose sum is σ = 41238604980. Its totient is φ = 10563385088.

The previous prime is 21205605679. The next prime is 21205605749. The reversal of 21205605712 is 21750650212.

It can be written as a sum of positive squares in 2 ways, for example, as 11706374416 + 9499231296 = 108196^2 + 97464^2 .

It is a super-2 number, since 2×21205605712² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2459173 + ... + 2467780.

It is an arithmetic number, because the mean of its divisors is an integer number (2061930249).

Almost surely, 2^21205605712 is an apocalyptic number.

It is an amenable number.

21205605712 is a deficient number, since it is larger than the sum of its proper divisors (20032999268).

21205605712 is a wasteful number, since it uses less digits than its factorization.

21205605712 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4927230 (or 4927224 counting only the distinct ones).

The product of its (nonzero) digits is 8400, while the sum is 31.

The spelling of 21205605712 in words is "twenty-one billion, two hundred five million, six hundred five thousand, seven hundred twelve".