21505248 has 72 divisors (see below), whose sum is σ = 61916400. Its totient is φ = 7079424.

The previous prime is 21505243. The next prime is 21505259. The reversal of 21505248 is 84250512.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (72).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21505241) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 25213 + ... + 26051.

It is an arithmetic number, because the mean of its divisors is an integer number (859950).

Almost surely, 2^21505248 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 21505248, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30958200).

21505248 is an abundant number, since it is smaller than the sum of its proper divisors (40411152).

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

21505248 is a wasteful number, since it uses less digits than its factorization.

21505248 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 944 (or 933 counting only the distinct ones).

The product of its (nonzero) digits is 3200, while the sum is 27.

The square root of 21505248 is about 4637.3751196124. The cubic root of 21505248 is about 278.0875110519.

The spelling of 21505248 in words is "twenty-one million, five hundred five thousand, two hundred forty-eight".