21521803 has 2 divisors, whose sum is σ = 21521804. Its totient is φ = 21521802.

The previous prime is 21521771. The next prime is 21521821. The reversal of 21521803 is 30812512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21521803 - 2⁵ = 21521771 is a prime.

It is not a weakly prime, because it can be changed into another prime (21521833) 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, 10760901 + 10760902.

It is an arithmetic number, because the mean of its divisors is an integer number (10760902).

Almost surely, 2^21521803 is an apocalyptic number.

21521803 is a deficient number, since it is larger than the sum of its proper divisors (1).

21521803 is an equidigital number, since it uses as much as digits as its factorization.

21521803 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 21521803 is about 4639.1597299511. The cubic root of 21521803 is about 278.1588511253.

The spelling of 21521803 in words is "twenty-one million, five hundred twenty-one thousand, eight hundred three".