21187520 has 56 divisors (see below), whose sum is σ = 51200304. Its totient is φ = 8349696.

The previous prime is 21187511. The next prime is 21187561. The reversal of 21187520 is 2578112.

It is a super-2 number, since 2×21187520² = 897822007500800, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21187520.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 22907 + ... + 23813.

Almost surely, 2^21187520 is an apocalyptic number.

21187520 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 21187520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25600152).

21187520 is an abundant number, since it is smaller than the sum of its proper divisors (30012784).

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

21187520 is an equidigital number, since it uses as much as digits as its factorization.

21187520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 997 (or 987 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 21187520 is about 4602.9903323818. The cubic root of 21187520 is about 276.7111813666.

The spelling of 21187520 in words is "twenty-one million, one hundred eighty-seven thousand, five hundred twenty".