21515120 has 80 divisors (see below), whose sum is σ = 56996352. Its totient is φ = 7476480.

The previous prime is 21515113. The next prime is 21515159. The reversal of 21515120 is 2151512.

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

It is a super-2 number, since 2×21515120² = 925800777228800, which contains 22 as substring.

It is a congruent number.

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, 19709 + ... + 20771.

Almost surely, 2^21515120 is an apocalyptic number.

21515120 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 21515120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28498176).

21515120 is an abundant number, since it is smaller than the sum of its proper divisors (35481232).

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

21515120 is a wasteful number, since it uses less digits than its factorization.

21515120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1110 (or 1104 counting only the distinct ones).

The product of its (nonzero) digits is 100, while the sum is 17.

The square root of 21515120 is about 4638.4393927268. The cubic root of 21515120 is about 278.1300566349.

Adding to 21515120 its reverse (2151512), we get a palindrome (23666632).

The spelling of 21515120 in words is "twenty-one million, five hundred fifteen thousand, one hundred twenty".