21201811 has 2 divisors, whose sum is σ = 21201812. Its totient is φ = 21201810.

The previous prime is 21201787. The next prime is 21201889. The reversal of 21201811 is 11810212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21201811 - 2¹³ = 21193619 is a prime.

It is not a weakly prime, because it can be changed into another prime (21201311) 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, 10600905 + 10600906.

It is an arithmetic number, because the mean of its divisors is an integer number (10600906).

Almost surely, 2^21201811 is an apocalyptic number.

21201811 is a deficient number, since it is larger than the sum of its proper divisors (1).

21201811 is an equidigital number, since it uses as much as digits as its factorization.

21201811 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21201811 is about 4604.5424311217. The cubic root of 21201811 is about 276.7733813586.

The spelling of 21201811 in words is "twenty-one million, two hundred one thousand, eight hundred eleven".