21531520 has 64 divisors (see below), whose sum is σ = 54529200. Its totient is φ = 8101888.

The previous prime is 21531493. The next prime is 21531527. The reversal of 21531520 is 2513512.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531527) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9891 + ... + 11869.

Almost surely, 2^21531520 is an apocalyptic number.

21531520 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 21531520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27264600).

21531520 is an abundant number, since it is smaller than the sum of its proper divisors (32997680).

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

21531520 is a wasteful number, since it uses less digits than its factorization.

21531520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2015 (or 2003 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 19.

The square root of 21531520 is about 4640.2068919392. The cubic root of 21531520 is about 278.2007073285.

The spelling of 21531520 in words is "twenty-one million, five hundred thirty-one thousand, five hundred twenty".