21561436753 has 8 divisors (see below), whose sum is σ = 22831095240. Its totient is φ = 20291927040.

The previous prime is 21561436717. The next prime is 21561436783. The reversal of 21561436753 is 35763416512.

It can be written as a sum of positive squares in 4 ways, for example, as 7484326144 + 14077110609 = 86512^2 + 118647^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21561436753 - 2⁹ = 21561436241 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21561436703) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 426373 + ... + 474253.

It is an arithmetic number, because the mean of its divisors is an integer number (2853886905).

Almost surely, 2^21561436753 is an apocalyptic number.

It is an amenable number.

21561436753 is a deficient number, since it is larger than the sum of its proper divisors (1269658487).

21561436753 is a wasteful number, since it uses less digits than its factorization.

21561436753 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74387.

The product of its digits is 453600, while the sum is 43.

The spelling of 21561436753 in words is "twenty-one billion, five hundred sixty-one million, four hundred thirty-six thousand, seven hundred fifty-three".