21015963648 has 384 divisors, whose sum is σ = 64959148800. Its totient is φ = 6709248000.

The previous prime is 21015963611. The next prime is 21015963653. The reversal of 21015963648 is 84636951012.

21015963648 is a `hidden beast` number, since 2 + 1 + 0 + 1 + 5 + 9 + 636 + 4 + 8 = 666.

It is a tau number, because it is divible by the number of its divisors (384).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 208078798 + ... + 208078898.

It is an arithmetic number, because the mean of its divisors is an integer number (169164450).

Almost surely, 2^21015963648 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 21015963648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32479574400).

21015963648 is an abundant number, since it is smaller than the sum of its proper divisors (43943185152).

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

21015963648 is a wasteful number, since it uses less digits than its factorization.

21015963648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 256 (or 230 counting only the distinct ones).

The product of its (nonzero) digits is 311040, while the sum is 45.

The spelling of 21015963648 in words is "twenty-one billion, fifteen million, nine hundred sixty-three thousand, six hundred forty-eight".