21006663252 has 12 divisors (see below), whose sum is σ = 49015547616. Its totient is φ = 7002221080.

The previous prime is 21006663221. The next prime is 21006663259. The reversal of 21006663252 is 25236660012.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21006663259) 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, 875277624 + ... + 875277647.

It is an arithmetic number, because the mean of its divisors is an integer number (4084628968).

Almost surely, 2^21006663252 is an apocalyptic number.

It is an amenable number.

21006663252 is an abundant number, since it is smaller than the sum of its proper divisors (28008884364).

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

21006663252 is a wasteful number, since it uses less digits than its factorization.

21006663252 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1750555278 (or 1750555276 counting only the distinct ones).

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

The spelling of 21006663252 in words is "twenty-one billion, six million, six hundred sixty-three thousand, two hundred fifty-two".