21581201 has 2 divisors, whose sum is σ = 21581202. Its totient is φ = 21581200.

The previous prime is 21581167. The next prime is 21581221. The reversal of 21581201 is 10218512.

It is a happy number.

It is an a-pointer prime, because the next prime (21581221) can be obtained adding 21581201 to its sum of digits (20).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21160000 + 421201 = 4600^2 + 649^2 .

It is a cyclic number.

It is not a de Polignac number, because 21581201 - 2⁶ = 21581137 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21581221) 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, 10790600 + 10790601.

It is an arithmetic number, because the mean of its divisors is an integer number (10790601).

Almost surely, 2^21581201 is an apocalyptic number.

It is an amenable number.

21581201 is a deficient number, since it is larger than the sum of its proper divisors (1).

21581201 is an equidigital number, since it uses as much as digits as its factorization.

21581201 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 160, while the sum is 20.

The square root of 21581201 is about 4645.5571248237. The cubic root of 21581201 is about 278.4145128364.

Adding to 21581201 its reverse (10218512), we get a palindrome (31799713).

The spelling of 21581201 in words is "twenty-one million, five hundred eighty-one thousand, two hundred one".