21355121 has 2 divisors, whose sum is σ = 21355122. Its totient is φ = 21355120.

The previous prime is 21355097. The next prime is 21355151. The reversal of 21355121 is 12155312.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19678096 + 1677025 = 4436^2 + 1295^2 .

It is a cyclic number.

It is not a de Polignac number, because 21355121 - 2⁶ = 21355057 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21355093 and 21355102.

It is not a weakly prime, because it can be changed into another prime (21355151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10677560 + 10677561.

It is an arithmetic number, because the mean of its divisors is an integer number (10677561).

Almost surely, 2^21355121 is an apocalyptic number.

It is an amenable number.

21355121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21355121 is an equidigital number, since it uses as much as digits as its factorization.

21355121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 300, while the sum is 20.

The square root of 21355121 is about 4621.1601357235. The cubic root of 21355121 is about 277.4388946429.

The spelling of 21355121 in words is "twenty-one million, three hundred fifty-five thousand, one hundred twenty-one".