21497219 has 4 divisors (see below), whose sum is σ = 21526896. Its totient is φ = 21467544.

The previous prime is 21497213. The next prime is 21497257. The reversal of 21497219 is 91279412.

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 21497219 - 2²⁴ = 4720003 is a prime.

It is a super-2 number, since 2×21497219² = 924260849467922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21497213) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13724 + ... + 15209.

It is an arithmetic number, because the mean of its divisors is an integer number (5381724).

Almost surely, 2^21497219 is an apocalyptic number.

21497219 is a deficient number, since it is larger than the sum of its proper divisors (29677).

21497219 is an equidigital number, since it uses as much as digits as its factorization.

21497219 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29676.

The product of its digits is 9072, while the sum is 35.

The square root of 21497219 is about 4636.5093551076. The cubic root of 21497219 is about 278.0528986858.

The spelling of 21497219 in words is "twenty-one million, four hundred ninety-seven thousand, two hundred nineteen".