21561120 has 384 divisors, whose sum is σ = 92897280. Its totient is φ = 4561920.

The previous prime is 21561107. The next prime is 21561131. The reversal of 21561120 is 2116512.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21561093 and 21561102.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 695505 + ... + 695535.

It is an arithmetic number, because the mean of its divisors is an integer number (241920).

Almost surely, 2^21561120 is an apocalyptic number.

21561120 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 21561120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (46448640).

21561120 is an abundant number, since it is smaller than the sum of its proper divisors (71336160).

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

21561120 is a wasteful number, since it uses less digits than its factorization.

21561120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85 (or 71 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 18.

The square root of 21561120 is about 4643.3953094691. The cubic root of 21561120 is about 278.3281324601.

Adding to 21561120 its reverse (2116512), we get a palindrome (23677632).

The spelling of 21561120 in words is "twenty-one million, five hundred sixty-one thousand, one hundred twenty".