21003387 has 8 divisors (see below), whose sum is σ = 28225536. Its totient is φ = 13891752.

The previous prime is 21003373. The next prime is 21003397. The reversal of 21003387 is 78330012.

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

It is not a de Polignac number, because 21003387 - 2⁴ = 21003371 is a prime.

It is a super-2 number, since 2×21003387² = 882284530943538, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21003397) by changing a digit.

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 in 7 ways as a sum of consecutive naturals, for example, 27183 + ... + 27944.

It is an arithmetic number, because the mean of its divisors is an integer number (3528192).

Almost surely, 2^21003387 is an apocalyptic number.

21003387 is a deficient number, since it is larger than the sum of its proper divisors (7222149).

21003387 is a wasteful number, since it uses less digits than its factorization.

21003387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55257.

The product of its (nonzero) digits is 1008, while the sum is 24.

The square root of 21003387 is about 4582.9452320533. The cubic root of 21003387 is about 275.9072493426.

Adding to 21003387 its reverse (78330012), we get a palindrome (99333399).

The spelling of 21003387 in words is "twenty-one million, three thousand, three hundred eighty-seven".