21726421 has 8 divisors (see below), whose sum is σ = 22722624. Its totient is φ = 20734560.

The previous prime is 21726403. The next prime is 21726427. The reversal of 21726421 is 12462712.

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

It is a cyclic number.

It is not a de Polignac number, because 21726421 - 2⁵ = 21726389 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21726427) 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, 13426 + ... + 14956.

It is an arithmetic number, because the mean of its divisors is an integer number (2840328).

Almost surely, 2^21726421 is an apocalyptic number.

It is an amenable number.

21726421 is a deficient number, since it is larger than the sum of its proper divisors (996203).

21726421 is a wasteful number, since it uses less digits than its factorization.

21726421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2171.

The product of its digits is 1344, while the sum is 25.

The square root of 21726421 is about 4661.1609068986. The cubic root of 21726421 is about 279.0376015062.

The spelling of 21726421 in words is "twenty-one million, seven hundred twenty-six thousand, four hundred twenty-one".