21545520 has 80 divisors (see below), whose sum is σ = 67495680. Its totient is φ = 5684992.

The previous prime is 21545509. The next prime is 21545551. The reversal of 21545520 is 2554512.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is a super-3 number, since 3×21545520³ (a number of 23 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (24).

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, 25261 + ... + 26099.

It is an arithmetic number, because the mean of its divisors is an integer number (843696).

Almost surely, 2^21545520 is an apocalyptic number.

21545520 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 21545520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33747840).

21545520 is an abundant number, since it is smaller than the sum of its proper divisors (45950160).

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

21545520 is a wasteful number, since it uses less digits than its factorization.

21545520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 962 (or 956 counting only the distinct ones).

The product of its (nonzero) digits is 2000, while the sum is 24.

The square root of 21545520 is about 4641.7152002250. The cubic root of 21545520 is about 278.2609905174.

The spelling of 21545520 in words is "twenty-one million, five hundred forty-five thousand, five hundred twenty".