21221008 has 10 divisors (see below), whose sum is σ = 41115734. Its totient is φ = 10610496.

The previous prime is 21221003. The next prime is 21221021. The reversal of 21221008 is 80012212.

It can be written as a sum of positive squares in only one way, i.e., 16257024 + 4963984 = 4032^2 + 2228^2 .

It is a Harshad number since it is a multiple of its sum of digits (16), and also a Moran number because the ratio is a prime number: 1326313 = 21221008 / (2 + 1 + 2 + 2 + 1 + 0 + 0 + 8).

It is a junction number, because it is equal to n+sod(n) for n = 21220982 and 21221000.

It is not an unprimeable number, because it can be changed into a prime (21221003) 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, 663141 + ... + 663172.

Almost surely, 2^21221008 is an apocalyptic number.

It is an amenable number.

21221008 is a deficient number, since it is larger than the sum of its proper divisors (19894726).

21221008 is a wasteful number, since it uses less digits than its factorization.

21221008 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1326321 (or 1326315 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 16.

The square root of 21221008 is about 4606.6265314219. The cubic root of 21221008 is about 276.8568901967.

The spelling of 21221008 in words is "twenty-one million, two hundred twenty-one thousand, eight".