21490217 has 4 divisors (see below), whose sum is σ = 24560256. Its totient is φ = 18420180.

The previous prime is 21490213. The next prime is 21490241. The reversal of 21490217 is 71209412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21490217 - 2² = 21490213 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21490213) 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, 1535009 + ... + 1535022.

It is an arithmetic number, because the mean of its divisors is an integer number (6140064).

Almost surely, 2^21490217 is an apocalyptic number.

It is an amenable number.

21490217 is a deficient number, since it is larger than the sum of its proper divisors (3070039).

21490217 is an equidigital number, since it uses as much as digits as its factorization.

21490217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3070038.

The product of its (nonzero) digits is 1008, while the sum is 26.

The square root of 21490217 is about 4635.7541996961. The cubic root of 21490217 is about 278.0227065973.

Adding to 21490217 its reverse (71209412), we get a palindrome (92699629).

The spelling of 21490217 in words is "twenty-one million, four hundred ninety thousand, two hundred seventeen".