21921505536 has 432 divisors, whose sum is σ = 71722324800. Its totient is φ = 5917556736.

The previous prime is 21921505513. The next prime is 21921505537. The reversal of 21921505536 is 63550512912.

It is a junction number, because it is equal to n+sod(n) for n = 21921505494 and 21921505503.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21921505537) 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, 57840195 + ... + 57840573.

It is an arithmetic number, because the mean of its divisors is an integer number (166023900).

Almost surely, 2^21921505536 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 21921505536, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35861162400).

21921505536 is an abundant number, since it is smaller than the sum of its proper divisors (49800819264).

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

21921505536 is a wasteful number, since it uses less digits than its factorization.

21921505536 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 494 (or 473 counting only the distinct ones).

The product of its (nonzero) digits is 81000, while the sum is 39.

The spelling of 21921505536 in words is "twenty-one billion, nine hundred twenty-one million, five hundred five thousand, five hundred thirty-six".