21205473705 has 64 divisors (see below), whose sum is σ = 41087934720. Its totient is φ = 10313768448.

The previous prime is 21205473701. The next prime is 21205473713. The reversal of 21205473705 is 50737450212.

21205473705 is a `hidden beast` number, since 21 + 20 + 547 + 3 + 70 + 5 = 666.

It is not a de Polignac number, because 21205473705 - 2² = 21205473701 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21205473705.

It is not an unprimeable number, because it can be changed into a prime (21205473701) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 72877 + ... + 218453.

It is an arithmetic number, because the mean of its divisors is an integer number (641998980).

Almost surely, 2^21205473705 is an apocalyptic number.

It is an amenable number.

21205473705 is a deficient number, since it is larger than the sum of its proper divisors (19882461015).

21205473705 is a wasteful number, since it uses less digits than its factorization.

21205473705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 145687 (or 145681 counting only the distinct ones).

The product of its (nonzero) digits is 58800, while the sum is 36.

The spelling of 21205473705 in words is "twenty-one billion, two hundred five million, four hundred seventy-three thousand, seven hundred five".