21115013506 has 32 divisors (see below), whose sum is σ = 34821414000. Its totient is φ = 9558054912.

The previous prime is 21115013503. The next prime is 21115013531. The reversal of 21115013506 is 60531051112.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 10991635281 + 10123378225 = 104841^2 + 100615^2 .

It is not an unprimeable number, because it can be changed into a prime (21115013503) 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, 225430 + ... + 305038.

Almost surely, 2^21115013506 is an apocalyptic number.

21115013506 is a deficient number, since it is larger than the sum of its proper divisors (13706400494).

21115013506 is a wasteful number, since it uses less digits than its factorization.

21115013506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79926.

The product of its (nonzero) digits is 900, while the sum is 25.

Adding to 21115013506 its reverse (60531051112), we get a palindrome (81646064618).

The spelling of 21115013506 in words is "twenty-one billion, one hundred fifteen million, thirteen thousand, five hundred six".