21056534549 has 4 divisors (see below), whose sum is σ = 21057135564. Its totient is φ = 21055933536.

The previous prime is 21056534501. The next prime is 21056534557. The reversal of 21056534549 is 94543565012.

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 5547568324 + 15508966225 = 74482^2 + 124535^2 .

It is a cyclic number.

It is not a de Polignac number, because 21056534549 - 2³² = 16761567253 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 (21056534579) 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, 244472 + ... + 319185.

It is an arithmetic number, because the mean of its divisors is an integer number (5264283891).

Almost surely, 2^21056534549 is an apocalyptic number.

It is an amenable number.

21056534549 is a deficient number, since it is larger than the sum of its proper divisors (601015).

21056534549 is an equidigital number, since it uses as much as digits as its factorization.

21056534549 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 601014.

The product of its (nonzero) digits is 648000, while the sum is 44.

The spelling of 21056534549 in words is "twenty-one billion, fifty-six million, five hundred thirty-four thousand, five hundred forty-nine".