21397328 has 10 divisors (see below), whose sum is σ = 41457354. Its totient is φ = 10698656.

The previous prime is 21397303. The next prime is 21397333. The reversal of 21397328 is 82379312.

It can be written as a sum of positive squares in only one way, i.e., 12588304 + 8809024 = 3548^2 + 2968^2 .

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 668651 + ... + 668682.

Almost surely, 2^21397328 is an apocalyptic number.

It is an amenable number.

21397328 is a deficient number, since it is larger than the sum of its proper divisors (20060026).

21397328 is a wasteful number, since it uses less digits than its factorization.

21397328 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1337341 (or 1337335 counting only the distinct ones).

The product of its digits is 18144, while the sum is 35.

The square root of 21397328 is about 4625.7245918883. The cubic root of 21397328 is about 277.6215543009.

The spelling of 21397328 in words is "twenty-one million, three hundred ninety-seven thousand, three hundred twenty-eight".