21801121 has 2 divisors, whose sum is σ = 21801122. Its totient is φ = 21801120.

The previous prime is 21801097. The next prime is 21801133. The reversal of 21801121 is 12110812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12680721 + 9120400 = 3561^2 + 3020^2 .

It is a cyclic number.

It is not a de Polignac number, because 21801121 - 2⁹ = 21800609 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21801095 and 21801104.

It is not a weakly prime, because it can be changed into another prime (21801161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10900560 + 10900561.

It is an arithmetic number, because the mean of its divisors is an integer number (10900561).

Almost surely, 2^21801121 is an apocalyptic number.

It is an amenable number.

21801121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21801121 is an equidigital number, since it uses as much as digits as its factorization.

21801121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 16.

The square root of 21801121 is about 4669.1670563388. The cubic root of 21801121 is about 279.3570323281.

Adding to 21801121 its reverse (12110812), we get a palindrome (33911933).

The spelling of 21801121 in words is "twenty-one million, eight hundred one thousand, one hundred twenty-one".