21644801 has 2 divisors, whose sum is σ = 21644802. Its totient is φ = 21644800.

The previous prime is 21644747. The next prime is 21644803. The reversal of 21644801 is 10844612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16192576 + 5452225 = 4024^2 + 2335^2 .

It is a cyclic number.

It is not a de Polignac number, because 21644801 - 2¹⁴ = 21628417 is a prime.

Together with 21644803, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21644803) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10822400 + 10822401.

It is an arithmetic number, because the mean of its divisors is an integer number (10822401).

Almost surely, 2^21644801 is an apocalyptic number.

It is an amenable number.

21644801 is a deficient number, since it is larger than the sum of its proper divisors (1).

21644801 is an equidigital number, since it uses as much as digits as its factorization.

21644801 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1536, while the sum is 26.

The square root of 21644801 is about 4652.3973390071. The cubic root of 21644801 is about 278.6877413290.

The spelling of 21644801 in words is "twenty-one million, six hundred forty-four thousand, eight hundred one".