21555803 has 2 divisors, whose sum is σ = 21555804. Its totient is φ = 21555802.

The previous prime is 21555799. The next prime is 21555811. The reversal of 21555803 is 30855512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21555803 - 2² = 21555799 is a prime.

It is not a weakly prime, because it can be changed into another prime (21555883) 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, 10777901 + 10777902.

It is an arithmetic number, because the mean of its divisors is an integer number (10777902).

Almost surely, 2^21555803 is an apocalyptic number.

21555803 is a deficient number, since it is larger than the sum of its proper divisors (1).

21555803 is an equidigital number, since it uses as much as digits as its factorization.

21555803 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6000, while the sum is 29.

The square root of 21555803 is about 4642.8227405319. The cubic root of 21555803 is about 278.3052518870.

The spelling of 21555803 in words is "twenty-one million, five hundred fifty-five thousand, eight hundred three".