21268640640 has 384 divisors, whose sum is σ = 74549311200. Its totient is φ = 5127045120.

The previous prime is 21268640639. The next prime is 21268640647. The reversal of 21268640640 is 4604686212.

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

It is a super-3 number, since 3×21268640640³ (a number of 32 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21268640647) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 92876046 + ... + 92876274.

Almost surely, 2^21268640640 is an apocalyptic number.

21268640640 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 21268640640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37274655600).

21268640640 is an abundant number, since it is smaller than the sum of its proper divisors (53280670560).

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

21268640640 is a wasteful number, since it uses less digits than its factorization.

21268640640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 386 (or 313 counting only the distinct ones).

The product of its (nonzero) digits is 110592, while the sum is 39.

The spelling of 21268640640 in words is "twenty-one billion, two hundred sixty-eight million, six hundred forty thousand, six hundred forty".