21006550016 has 44 divisors (see below), whose sum is σ = 42149244780. Its totient is φ = 10464092160.

The previous prime is 21006550013. The next prime is 21006550027. The reversal of 21006550016 is 61005560012.

It can be written as a sum of positive squares in 2 ways, for example, as 5207065600 + 15799484416 = 72160^2 + 125696^2 .

It is not an unprimeable number, because it can be changed into a prime (21006550013) 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, 237326 + ... + 313586.

Almost surely, 2^21006550016 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21006550016, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21074622390).

21006550016 is an abundant number, since it is smaller than the sum of its proper divisors (21142694764).

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

21006550016 is an equidigital number, since it uses as much as digits as its factorization.

21006550016 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76550 (or 76532 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 26.

The spelling of 21006550016 in words is "twenty-one billion, six million, five hundred fifty thousand, sixteen".