21506220636 has 96 divisors (see below), whose sum is σ = 51819264000. Its totient is φ = 6939522240.

The previous prime is 21506220563. The next prime is 21506220653. The reversal of 21506220636 is 63602260512.

It is a junction number, because it is equal to n+sod(n) for n = 21506220597 and 21506220606.

It is a congruent number.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 12657315 + ... + 12659013.

It is an arithmetic number, because the mean of its divisors is an integer number (539784000).

Almost surely, 2^21506220636 is an apocalyptic number.

It is an amenable number.

21506220636 is an abundant number, since it is smaller than the sum of its proper divisors (30313043364).

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

21506220636 is a wasteful number, since it uses less digits than its factorization.

21506220636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2039 (or 2037 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 33.

The spelling of 21506220636 in words is "twenty-one billion, five hundred six million, two hundred twenty thousand, six hundred thirty-six".