21615760 has 40 divisors (see below), whose sum is σ = 50606136. Its totient is φ = 8586240.

The previous prime is 21615719. The next prime is 21615761. The reversal of 21615760 is 6751612.

It can be written as a sum of positive squares in 4 ways, for example, as 2396304 + 19219456 = 1548^2 + 4384^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is not an unprimeable number, because it can be changed into a prime (21615761) 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, 11700 + ... + 13420.

Almost surely, 2^21615760 is an apocalyptic number.

21615760 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 21615760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25303068).

21615760 is an abundant number, since it is smaller than the sum of its proper divisors (28990376).

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

21615760 is a wasteful number, since it uses less digits than its factorization.

21615760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1891 (or 1885 counting only the distinct ones).

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 21615760 is about 4649.2752123315. The cubic root of 21615760 is about 278.5630463650.

It can be divided in two parts, 2161 and 5760, that added together give a square (7921 = 89²).

The spelling of 21615760 in words is "twenty-one million, six hundred fifteen thousand, seven hundred sixty".