21726641 has 4 divisors (see below), whose sum is σ = 21777252. Its totient is φ = 21676032.

The previous prime is 21726613. The next prime is 21726701. The reversal of 21726641 is 14662712.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14409616 + 7317025 = 3796^2 + 2705^2 .

It is a cyclic number.

It is not a de Polignac number, because 21726641 - 2¹⁰ = 21725617 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21726611) 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, 24656 + ... + 25521.

It is an arithmetic number, because the mean of its divisors is an integer number (5444313).

Almost surely, 2^21726641 is an apocalyptic number.

It is an amenable number.

21726641 is a deficient number, since it is larger than the sum of its proper divisors (50611).

21726641 is an equidigital number, since it uses as much as digits as its factorization.

21726641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50610.

The product of its digits is 4032, while the sum is 29.

The square root of 21726641 is about 4661.1845061100. The cubic root of 21726641 is about 279.0385433405.

The spelling of 21726641 in words is "twenty-one million, seven hundred twenty-six thousand, six hundred forty-one".