21520266643 has 16 divisors (see below), whose sum is σ = 22055997600. Its totient is φ = 20992167936.

The previous prime is 21520266613. The next prime is 21520266721. The reversal of 21520266643 is 34666202512.

It is a cyclic number.

It is not a de Polignac number, because 21520266643 - 2¹³ = 21520258451 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21520266613) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3676383 + ... + 3682231.

It is an arithmetic number, because the mean of its divisors is an integer number (1378499850).

Almost surely, 2^21520266643 is an apocalyptic number.

21520266643 is a deficient number, since it is larger than the sum of its proper divisors (535730957).

21520266643 is an equidigital number, since it uses as much as digits as its factorization.

21520266643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6486.

The product of its (nonzero) digits is 103680, while the sum is 37.

The spelling of 21520266643 in words is "twenty-one billion, five hundred twenty million, two hundred sixty-six thousand, six hundred forty-three".