21006224 has 10 divisors (see below), whose sum is σ = 40699590. Its totient is φ = 10503104.

The previous prime is 21006217. The next prime is 21006233. The reversal of 21006224 is 42260012.

It can be written as a sum of positive squares in only one way, i.e., 13542400 + 7463824 = 3680^2 + 2732^2 .

It is a super-2 number, since 2×21006224² = 882522893476352, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 656429 + ... + 656460.

It is an arithmetic number, because the mean of its divisors is an integer number (4069959).

Almost surely, 2^21006224 is an apocalyptic number.

It is an amenable number.

21006224 is a deficient number, since it is larger than the sum of its proper divisors (19693366).

21006224 is a wasteful number, since it uses less digits than its factorization.

21006224 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1312897 (or 1312891 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 17.

The square root of 21006224 is about 4583.2547387201. The cubic root of 21006224 is about 275.9196713650.

Adding to 21006224 its reverse (42260012), we get a palindrome (63266236).

The spelling of 21006224 in words is "twenty-one million, six thousand, two hundred twenty-four".