21205530745 has 32 divisors (see below), whose sum is σ = 29265175296. Its totient is φ = 14449536000.

The previous prime is 21205530739. The next prime is 21205530757. The reversal of 21205530745 is 54703550212.

It is not a de Polignac number, because 21205530745 - 2¹³ = 21205522553 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21205530745.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4772725 + ... + 4777165.

It is an arithmetic number, because the mean of its divisors is an integer number (914536728).

Almost surely, 2^21205530745 is an apocalyptic number.

It is an amenable number.

21205530745 is a deficient number, since it is larger than the sum of its proper divisors (8059644551).

21205530745 is a wasteful number, since it uses less digits than its factorization.

21205530745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5281.

The product of its (nonzero) digits is 42000, while the sum is 34.

The spelling of 21205530745 in words is "twenty-one billion, two hundred five million, five hundred thirty thousand, seven hundred forty-five".