21561336 has 64 divisors (see below), whose sum is σ = 60343200. Its totient is φ = 7133184.

The previous prime is 21561329. The next prime is 21561341. The reversal of 21561336 is 63316512.

21561336 is a `hidden beast` number, since 2 + 15 + 613 + 36 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

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, 37080 + ... + 37656.

Almost surely, 2^21561336 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21561336, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30171600).

21561336 is an abundant number, since it is smaller than the sum of its proper divisors (38781864).

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

21561336 is a wasteful number, since it uses less digits than its factorization.

21561336 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 765 (or 755 counting only the distinct ones).

The product of its digits is 3240, while the sum is 27.

The square root of 21561336 is about 4643.4185682534. The cubic root of 21561336 is about 278.3290618904.

Adding to 21561336 its reverse (63316512), we get a palindrome (84877848).

The spelling of 21561336 in words is "twenty-one million, five hundred sixty-one thousand, three hundred thirty-six".