21509409820803 has 4 divisors (see below), whose sum is σ = 28679213094408. Its totient is φ = 14339606547200.

The previous prime is 21509409820781. The next prime is 21509409820813. The reversal of 21509409820803 is 30802890490512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21509409820803 - 2¹⁷ = 21509409689731 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21509409820813) 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, 3584901636798 + ... + 3584901636803.

It is an arithmetic number, because the mean of its divisors is an integer number (7169803273602).

Almost surely, 2^{21509409820803} is an apocalyptic number.

21509409820803 is a deficient number, since it is larger than the sum of its proper divisors (7169803273605).

21509409820803 is an equidigital number, since it uses as much as digits as its factorization.

21509409820803 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7169803273604.

The product of its (nonzero) digits is 1244160, while the sum is 51.

The spelling of 21509409820803 in words is "twenty-one trillion, five hundred nine billion, four hundred nine million, eight hundred twenty thousand, eight hundred three".