21265240403 has 16 divisors (see below), whose sum is σ = 23651489376. Its totient is φ = 18954973440.

The previous prime is 21265240397. The next prime is 21265240411. The reversal of 21265240403 is 30404256212.

It is a cyclic number.

It is not a de Polignac number, because 21265240403 - 2¹⁰ = 21265239379 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21265240453) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 955025 + ... + 977037.

It is an arithmetic number, because the mean of its divisors is an integer number (1478218086).

Almost surely, 2^21265240403 is an apocalyptic number.

21265240403 is a deficient number, since it is larger than the sum of its proper divisors (2386248973).

21265240403 is a wasteful number, since it uses less digits than its factorization.

21265240403 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23734.

The product of its (nonzero) digits is 11520, while the sum is 29.

Adding to 21265240403 its reverse (30404256212), we get a palindrome (51669496615).

The spelling of 21265240403 in words is "twenty-one billion, two hundred sixty-five million, two hundred forty thousand, four hundred three".