21517219 has 4 divisors (see below), whose sum is σ = 21739144. Its totient is φ = 21295296.

The previous prime is 21517187. The next prime is 21517231. The reversal of 21517219 is 91271512.

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 21517219 - 2⁵ = 21517187 is a prime.

It is a super-2 number, since 2×21517219² = 925981426987922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21517289) 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, 110817 + ... + 111010.

It is an arithmetic number, because the mean of its divisors is an integer number (5434786).

Almost surely, 2^21517219 is an apocalyptic number.

21517219 is a deficient number, since it is larger than the sum of its proper divisors (221925).

21517219 is an equidigital number, since it uses as much as digits as its factorization.

21517219 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 221924.

The product of its digits is 1260, while the sum is 28.

The square root of 21517219 is about 4638.6656486537. The cubic root of 21517219 is about 278.1391010651.

It can be divided in two parts, 21517 and 219, that added together give a triangular number (21736 = T₂₀₈).

The spelling of 21517219 in words is "twenty-one million, five hundred seventeen thousand, two hundred nineteen".