21505332403 has 4 divisors (see below), whose sum is σ = 21613399600. Its totient is φ = 21397265208.

The previous prime is 21505332379. The next prime is 21505332439. The reversal of 21505332403 is 30423350512.

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 21505332403 - 2²⁹ = 20968461491 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21505332203) 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, 54033300 + ... + 54033697.

It is an arithmetic number, because the mean of its divisors is an integer number (5403349900).

Almost surely, 2^21505332403 is an apocalyptic number.

21505332403 is a deficient number, since it is larger than the sum of its proper divisors (108067197).

21505332403 is a wasteful number, since it uses less digits than its factorization.

21505332403 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 108067196.

The product of its (nonzero) digits is 10800, while the sum is 28.

Adding to 21505332403 its reverse (30423350512), we get a palindrome (51928682915).

It can be divided in two parts, 215053 and 32403, that added together give a triangular number (247456 = T₇₀₃).

The spelling of 21505332403 in words is "twenty-one billion, five hundred five million, three hundred thirty-two thousand, four hundred three".