21523695648 has 384 divisors, whose sum is σ = 75637836288. Its totient is φ = 5196939264.

The previous prime is 21523695581. The next prime is 21523695673. The reversal of 21523695648 is 84659632512.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is a self number, because there is not a number n which added to its sum of digits gives 21523695648.

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 63 ways as a sum of consecutive naturals, for example, 5492986 + ... + 5496902.

It is an arithmetic number, because the mean of its divisors is an integer number (196973532).

Almost surely, 2^21523695648 is an apocalyptic number.

21523695648 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21523695648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37818918144).

21523695648 is an abundant number, since it is smaller than the sum of its proper divisors (54114140640).

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

21523695648 is a wasteful number, since it uses less digits than its factorization.

21523695648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4004 (or 3996 counting only the distinct ones).

The product of its digits is 3110400, while the sum is 51.

The spelling of 21523695648 in words is "twenty-one billion, five hundred twenty-three million, six hundred ninety-five thousand, six hundred forty-eight".