21800081 has 2 divisors, whose sum is σ = 21800082. Its totient is φ = 21800080.

The previous prime is 21800059. The next prime is 21800089. The reversal of 21800081 is 18000812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11662225 + 10137856 = 3415^2 + 3184^2 .

It is a cyclic number.

It is not a de Polignac number, because 21800081 - 2⁶ = 21800017 is a prime.

It is a super-2 number, since 2×21800081² = 950487063213122, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21800089) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10900040 + 10900041.

It is an arithmetic number, because the mean of its divisors is an integer number (10900041).

Almost surely, 2^21800081 is an apocalyptic number.

It is an amenable number.

21800081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21800081 is an equidigital number, since it uses as much as digits as its factorization.

21800081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 128, while the sum is 20.

The square root of 21800081 is about 4669.0556861104. The cubic root of 21800081 is about 279.3525901111.

Adding to 21800081 its reverse (18000812), we get a palindrome (39800893).

The spelling of 21800081 in words is "twenty-one million, eight hundred thousand, eighty-one".