21305515206 has 16 divisors (see below), whose sum is σ = 42654656304. Its totient is φ = 7094567424.

The previous prime is 21305515169. The next prime is 21305515207. The reversal of 21305515206 is 60251550312.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21305515207) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1811395 + ... + 1823118.

It is an arithmetic number, because the mean of its divisors is an integer number (2665916019).

Almost surely, 2^21305515206 is an apocalyptic number.

21305515206 is an abundant number, since it is smaller than the sum of its proper divisors (21349141098).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21305515206 is a wasteful number, since it uses less digits than its factorization.

21305515206 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3635495.

The product of its (nonzero) digits is 9000, while the sum is 30.

The spelling of 21305515206 in words is "twenty-one billion, three hundred five million, five hundred fifteen thousand, two hundred six".