21205742273 has 4 divisors (see below), whose sum is σ = 21206461380. Its totient is φ = 21205023168.

The previous prime is 21205742269. The next prime is 21205742291. The reversal of 21205742273 is 37224750212.

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

It can be written as a sum of positive squares in 2 ways, for example, as 9160021264 + 12045721009 = 95708^2 + 109753^2 .

It is a cyclic number.

It is not a de Polignac number, because 21205742273 - 2² = 21205742269 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21205742213) 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, 313340 + ... + 374957.

It is an arithmetic number, because the mean of its divisors is an integer number (5301615345).

Almost surely, 2^21205742273 is an apocalyptic number.

It is an amenable number.

21205742273 is a deficient number, since it is larger than the sum of its proper divisors (719107).

21205742273 is an equidigital number, since it uses as much as digits as its factorization.

21205742273 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 719106.

The product of its (nonzero) digits is 47040, while the sum is 35.

The spelling of 21205742273 in words is "twenty-one billion, two hundred five million, seven hundred forty-two thousand, two hundred seventy-three".