21553516 has 12 divisors (see below), whose sum is σ = 37811200. Its totient is φ = 10750320.

The previous prime is 21553487. The next prime is 21553517. The reversal of 21553516 is 61535512.

It is not an unprimeable number, because it can be changed into a prime (21553517) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4716 + ... + 8083.

Almost surely, 2^21553516 is an apocalyptic number.

It is an amenable number.

21553516 is a deficient number, since it is larger than the sum of its proper divisors (16257684).

21553516 is a wasteful number, since it uses less digits than its factorization.

21553516 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13224 (or 13222 counting only the distinct ones).

The product of its digits is 4500, while the sum is 28.

The square root of 21553516 is about 4642.5764398661. The cubic root of 21553516 is about 278.2954091141.

It can be divided in two parts, 2155 and 3516, that added together give a triangular number (5671 = T₁₀₆).

The spelling of 21553516 in words is "twenty-one million, five hundred fifty-three thousand, five hundred sixteen".