21716421 has 8 divisors (see below), whose sum is σ = 28991424. Its totient is φ = 14459520.

The previous prime is 21716413. The next prime is 21716437. The reversal of 21716421 is 12461712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21716421 - 2³ = 21716413 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21716391 and 21716400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21716441) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1420 + ... + 6741.

It is an arithmetic number, because the mean of its divisors is an integer number (3623928).

Almost surely, 2^21716421 is an apocalyptic number.

It is an amenable number.

21716421 is a deficient number, since it is larger than the sum of its proper divisors (7275003).

21716421 is an equidigital number, since it uses as much as digits as its factorization.

21716421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9051.

The product of its digits is 672, while the sum is 24.

The square root of 21716421 is about 4660.0880892962. The cubic root of 21716421 is about 278.9947841422.

The spelling of 21716421 in words is "twenty-one million, seven hundred sixteen thousand, four hundred twenty-one".