21388330 has 8 divisors (see below), whose sum is σ = 38499012. Its totient is φ = 8555328.

The previous prime is 21388327. The next prime is 21388333. The reversal of 21388330 is 3388312.

It is an interprime number because it is at equal distance from previous prime (21388327) and next prime (21388333).

It can be written as a sum of positive squares in 2 ways, for example, as 21095649 + 292681 = 4593^2 + 541^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21388333) 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 3 ways as a sum of consecutive naturals, for example, 1069407 + ... + 1069426.

Almost surely, 2^21388330 is an apocalyptic number.

21388330 is a deficient number, since it is larger than the sum of its proper divisors (17110682).

21388330 is a wasteful number, since it uses less digits than its factorization.

21388330 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2138840.

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 21388330 is about 4624.7518852367. The cubic root of 21388330 is about 277.5826337250.

The spelling of 21388330 in words is "twenty-one million, three hundred eighty-eight thousand, three hundred thirty".