21217007 has 4 divisors (see below), whose sum is σ = 24248016. Its totient is φ = 18186000.

The previous prime is 21216997. The next prime is 21217019. The reversal of 21217007 is 70071212.

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

It is not a de Polignac number, because 21217007 - 2⁴ = 21216991 is a prime.

It is a super-2 number, since 2×21217007² = 900322772076098, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21217007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21217087) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1515494 + ... + 1515507.

It is an arithmetic number, because the mean of its divisors is an integer number (6062004).

Almost surely, 2^21217007 is an apocalyptic number.

21217007 is a deficient number, since it is larger than the sum of its proper divisors (3031009).

21217007 is an equidigital number, since it uses as much as digits as its factorization.

21217007 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3031008.

The product of its (nonzero) digits is 196, while the sum is 20.

The square root of 21217007 is about 4606.1922452282. The cubic root of 21217007 is about 276.8394896089.

Adding to 21217007 its reverse (70071212), we get a palindrome (91288219).

The spelling of 21217007 in words is "twenty-one million, two hundred seventeen thousand, seven".