21205473727 has 4 divisors (see below), whose sum is σ = 21206405880. Its totient is φ = 21204541576.

The previous prime is 21205473713. The next prime is 21205473739. The reversal of 21205473727 is 72737450212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21205473727 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21205473727.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21205473767) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 431077 + ... + 477742.

It is an arithmetic number, because the mean of its divisors is an integer number (5301601470).

Almost surely, 2^21205473727 is an apocalyptic number.

21205473727 is a deficient number, since it is larger than the sum of its proper divisors (932153).

21205473727 is an equidigital number, since it uses as much as digits as its factorization.

21205473727 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 932152.

The product of its (nonzero) digits is 164640, while the sum is 40.

The spelling of 21205473727 in words is "twenty-one billion, two hundred five million, four hundred seventy-three thousand, seven hundred twenty-seven".