21420716533 has 4 divisors (see below), whose sum is σ = 22680758700. Its totient is φ = 20160674368.

The previous prime is 21420716503. The next prime is 21420716549. The reversal of 21420716533 is 33561702412.

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 6644369169 + 14776347364 = 81513^2 + 121558^2 .

It is a cyclic number.

It is not a de Polignac number, because 21420716533 - 2⁹ = 21420716021 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21420716503) 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, 630021058 + ... + 630021091.

It is an arithmetic number, because the mean of its divisors is an integer number (5670189675).

Almost surely, 2^21420716533 is an apocalyptic number.

It is an amenable number.

21420716533 is a deficient number, since it is larger than the sum of its proper divisors (1260042167).

21420716533 is a wasteful number, since it uses less digits than its factorization.

21420716533 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1260042166.

The product of its (nonzero) digits is 30240, while the sum is 34.

The spelling of 21420716533 in words is "twenty-one billion, four hundred twenty million, seven hundred sixteen thousand, five hundred thirty-three".