21520140305 has 4 divisors (see below), whose sum is σ = 25824168372. Its totient is φ = 17216112240.

The previous prime is 21520140293. The next prime is 21520140347. The reversal of 21520140305 is 50304102512.

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 16253445121 + 5266695184 = 127489^2 + 72572^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21520140305 is a prime.

It is a Duffinian 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, 2152014026 + ... + 2152014035.

It is an arithmetic number, because the mean of its divisors is an integer number (6456042093).

Almost surely, 2^21520140305 is an apocalyptic number.

It is an amenable number.

21520140305 is a deficient number, since it is larger than the sum of its proper divisors (4304028067).

21520140305 is an equidigital number, since it uses as much as digits as its factorization.

21520140305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4304028066.

The product of its (nonzero) digits is 1200, while the sum is 23.

Adding to 21520140305 its reverse (50304102512), we get a palindrome (71824242817).

The spelling of 21520140305 in words is "twenty-one billion, five hundred twenty million, one hundred forty thousand, three hundred five".