21003207 has 4 divisors (see below), whose sum is σ = 28004280. Its totient is φ = 14002136.

The previous prime is 21003179. The next prime is 21003223. The reversal of 21003207 is 70230012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21003207 - 2⁷ = 21003079 is a prime.

It is a super-2 number, since 2×21003207² = 882269408569698, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21003247) 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 3 ways as a sum of consecutive naturals, for example, 3500532 + ... + 3500537.

It is an arithmetic number, because the mean of its divisors is an integer number (7001070).

Almost surely, 2^21003207 is an apocalyptic number.

21003207 is a deficient number, since it is larger than the sum of its proper divisors (7001073).

21003207 is an equidigital number, since it uses as much as digits as its factorization.

21003207 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7001072.

The product of its (nonzero) digits is 84, while the sum is 15.

The square root of 21003207 is about 4582.9255939847. The cubic root of 21003207 is about 275.9064611611.

Adding to 21003207 its reverse (70230012), we get a palindrome (91233219).

The spelling of 21003207 in words is "twenty-one million, three thousand, two hundred seven".