21319217 has 4 divisors (see below), whose sum is σ = 21328896. Its totient is φ = 21309540.

The previous prime is 21319211. The next prime is 21319219. The reversal of 21319217 is 71291312.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21319217 - 2⁸ = 21318961 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21319211) 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, 248 + ... + 6534.

It is an arithmetic number, because the mean of its divisors is an integer number (5332224).

Almost surely, 2^21319217 is an apocalyptic number.

It is an amenable number.

21319217 is a deficient number, since it is larger than the sum of its proper divisors (9679).

21319217 is an equidigital number, since it uses as much as digits as its factorization.

21319217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9678.

The product of its digits is 756, while the sum is 26.

The square root of 21319217 is about 4617.2737627306. The cubic root of 21319217 is about 277.2833229995.

The spelling of 21319217 in words is "twenty-one million, three hundred nineteen thousand, two hundred seventeen".