21065685503 has 4 divisors (see below), whose sum is σ = 21422731080. Its totient is φ = 20708639928.

The previous prime is 21065685401. The next prime is 21065685517. The reversal of 21065685503 is 30558656012.

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 21065685503 - 2¹² = 21065681407 is a prime.

It is a super-2 number, since 2×21065685503² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21065675503) 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, 178522700 + ... + 178522817.

It is an arithmetic number, because the mean of its divisors is an integer number (5355682770).

Almost surely, 2^21065685503 is an apocalyptic number.

21065685503 is a deficient number, since it is larger than the sum of its proper divisors (357045577).

21065685503 is an equidigital number, since it uses as much as digits as its factorization.

21065685503 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 357045576.

The product of its (nonzero) digits is 216000, while the sum is 41.

The spelling of 21065685503 in words is "twenty-one billion, sixty-five million, six hundred eighty-five thousand, five hundred three".