21201521824 has 96 divisors (see below), whose sum is σ = 48103735680. Its totient is φ = 9010434048.

The previous prime is 21201521801. The next prime is 21201521827. The reversal of 21201521824 is 42812510212.

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

It is a junction number, because it is equal to n+sod(n) for n = 21201521792 and 21201521801.

It is not an unprimeable number, because it can be changed into a prime (21201521827) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24738804 + ... + 24739660.

It is an arithmetic number, because the mean of its divisors is an integer number (501080580).

Almost surely, 2^21201521824 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 21201521824, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24051867840).

21201521824 is an abundant number, since it is smaller than the sum of its proper divisors (26902213856).

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

21201521824 is a wasteful number, since it uses less digits than its factorization.

21201521824 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1670 (or 1662 counting only the distinct ones).

The product of its (nonzero) digits is 2560, while the sum is 28.

The spelling of 21201521824 in words is "twenty-one billion, two hundred one million, five hundred twenty-one thousand, eight hundred twenty-four".