21551224 has 8 divisors (see below), whose sum is σ = 40408560. Its totient is φ = 10775608.

The previous prime is 21551221. The next prime is 21551251. The reversal of 21551224 is 42215512.

It is a tau number, because it is divible by the number of its divisors (8).

It is a junction number, because it is equal to n+sod(n) for n = 21551195 and 21551204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21551221) 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 as a sum of consecutive naturals, namely, 1346944 + ... + 1346959.

It is an arithmetic number, because the mean of its divisors is an integer number (5051070).

Almost surely, 2^21551224 is an apocalyptic number.

It is an amenable number.

21551224 is a deficient number, since it is larger than the sum of its proper divisors (18857336).

21551224 is a wasteful number, since it uses less digits than its factorization.

21551224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2693909 (or 2693905 counting only the distinct ones).

The product of its digits is 800, while the sum is 22.

The square root of 21551224 is about 4642.3295876101. The cubic root of 21551224 is about 278.2855441236.

Adding to 21551224 its reverse (42215512), we get a palindrome (63766736).

The spelling of 21551224 in words is "twenty-one million, five hundred fifty-one thousand, two hundred twenty-four".