21921008640 has 176 divisors, whose sum is σ = 70433044992. Its totient is φ = 5818925056.

The previous prime is 21921008591. The next prime is 21921008687. The reversal of 21921008640 is 4680012912.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3483577 + ... + 3489863.

Almost surely, 2^21921008640 is an apocalyptic number.

21921008640 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 21921008640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35216522496).

21921008640 is an abundant number, since it is smaller than the sum of its proper divisors (48512036352).

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

21921008640 is a wasteful number, since it uses less digits than its factorization.

21921008640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6542 (or 6524 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 33.

The spelling of 21921008640 in words is "twenty-one billion, nine hundred twenty-one million, eight thousand, six hundred forty".