21404217 has 4 divisors (see below), whose sum is σ = 28538960. Its totient is φ = 14269476.

The previous prime is 21404213. The next prime is 21404263. The reversal of 21404217 is 71240412.

It is a happy number.

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 not a de Polignac number, because 21404217 - 2² = 21404213 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21404193 and 21404202.

It is not an unprimeable number, because it can be changed into a prime (21404213) 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, 3567367 + ... + 3567372.

It is an arithmetic number, because the mean of its divisors is an integer number (7134740).

Almost surely, 2^21404217 is an apocalyptic number.

It is an amenable number.

21404217 is a deficient number, since it is larger than the sum of its proper divisors (7134743).

21404217 is an equidigital number, since it uses as much as digits as its factorization.

21404217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7134742.

The product of its (nonzero) digits is 448, while the sum is 21.

The square root of 21404217 is about 4626.4691720577. The cubic root of 21404217 is about 277.6513450871.

Adding to 21404217 its reverse (71240412), we get a palindrome (92644629).

The spelling of 21404217 in words is "twenty-one million, four hundred four thousand, two hundred seventeen".