21638801 has 2 divisors, whose sum is σ = 21638802. Its totient is φ = 21638800.

The previous prime is 21638797. The next prime is 21638803. The reversal of 21638801 is 10883612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21613201 + 25600 = 4649^2 + 160^2 .

It is a cyclic number.

It is not a de Polignac number, because 21638801 - 2² = 21638797 is a prime.

It is a Sophie Germain prime.

Together with 21638803, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21638803) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10819400 + 10819401.

It is an arithmetic number, because the mean of its divisors is an integer number (10819401).

Almost surely, 2^21638801 is an apocalyptic number.

It is an amenable number.

21638801 is a deficient number, since it is larger than the sum of its proper divisors (1).

21638801 is an equidigital number, since it uses as much as digits as its factorization.

21638801 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2304, while the sum is 29.

The square root of 21638801 is about 4651.7524654693. The cubic root of 21638801 is about 278.6619879394.

The spelling of 21638801 in words is "twenty-one million, six hundred thirty-eight thousand, eight hundred one".