21536840640 has 336 divisors, whose sum is σ = 79830302112. Its totient is φ = 4904976384.

The previous prime is 21536840627. The next prime is 21536840669. The reversal of 21536840640 is 4604863512.

It is a tau number, because it is divible by the number of its divisors (336).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 16604472 + ... + 16605768.

Almost surely, 2^21536840640 is an apocalyptic number.

21536840640 is a gapful number since it is divisible by the number (20) 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 21536840640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39915151056).

21536840640 is an abundant number, since it is smaller than the sum of its proper divisors (58293461472).

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

21536840640 is a wasteful number, since it uses less digits than its factorization.

21536840640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1684 (or 1667 counting only the distinct ones).

The product of its (nonzero) digits is 138240, while the sum is 39.

The spelling of 21536840640 in words is "twenty-one billion, five hundred thirty-six million, eight hundred forty thousand, six hundred forty".