21135205504 has 64 divisors (see below), whose sum is σ = 48149173440. Its totient is φ = 9052517376.

The previous prime is 21135205459. The next prime is 21135205577. The reversal of 21135205504 is 40550253112.

It is a tau number, because it is divible by the number of its divisors (64).

It is a Harshad number since it is a multiple of its sum of digits (28).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1725867 + ... + 1738069.

It is an arithmetic number, because the mean of its divisors is an integer number (752330835).

Almost surely, 2^21135205504 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 21135205504, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24074586720).

21135205504 is an abundant number, since it is smaller than the sum of its proper divisors (27013967936).

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

21135205504 is a wasteful number, since it uses less digits than its factorization.

21135205504 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14157 (or 14145 counting only the distinct ones).

The product of its (nonzero) digits is 6000, while the sum is 28.

Adding to 21135205504 its reverse (40550253112), we get a palindrome (61685458616).

The spelling of 21135205504 in words is "twenty-one billion, one hundred thirty-five million, two hundred five thousand, five hundred four".