21551316 has 24 divisors (see below), whose sum is σ = 51646560. Its totient is φ = 6989472.

The previous prime is 21551303. The next prime is 21551317. The reversal of 21551316 is 61315512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21551317) 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 7 ways as a sum of consecutive naturals, for example, 23826 + ... + 24713.

It is an arithmetic number, because the mean of its divisors is an integer number (2151940).

Almost surely, 2^21551316 is an apocalyptic number.

It is an amenable number.

21551316 is an abundant number, since it is smaller than the sum of its proper divisors (30095244).

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

21551316 is a wasteful number, since it uses less digits than its factorization.

21551316 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48583 (or 48581 counting only the distinct ones).

The product of its digits is 900, while the sum is 24.

The square root of 21551316 is about 4642.3394964177. The cubic root of 21551316 is about 278.2859401140.

Adding to 21551316 its reverse (61315512), we get a palindrome (82866828).

The spelling of 21551316 in words is "twenty-one million, five hundred fifty-one thousand, three hundred sixteen".