21561480 has 96 divisors (see below), whose sum is σ = 70887960. Its totient is φ = 5683200.

The previous prime is 21561479. The next prime is 21561481. The reversal of 21561480 is 8416512.

21561480 is a `hidden beast` number, since 21 + 561 + 4 + 80 = 666.

It is an interprime number because it is at equal distance from previous prime (21561479) and next prime (21561481).

It can be written as a sum of positive squares in 4 ways, for example, as 21288996 + 272484 = 4614^2 + 522^2 .

It is not an unprimeable number, because it can be changed into a prime (21561481) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 36064 + ... + 36656.

Almost surely, 2^21561480 is an apocalyptic number.

21561480 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 21561480, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35443980).

21561480 is an abundant number, since it is smaller than the sum of its proper divisors (49326480).

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

21561480 is a wasteful number, since it uses less digits than its factorization.

21561480 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 711 (or 704 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 21561480 is about 4643.4340740448. The cubic root of 21561480 is about 278.3296815071.

Adding to 21561480 its reverse (8416512), we get a palindrome (29977992).

The spelling of 21561480 in words is "twenty-one million, five hundred sixty-one thousand, four hundred eighty".