21939811 has 2 divisors, whose sum is σ = 21939812. Its totient is φ = 21939810.

The previous prime is 21939791. The next prime is 21939817. The reversal of 21939811 is 11893912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21939811 - 2⁷ = 21939683 is a prime.

It is a super-3 number, since 3×21939811³ (a number of 23 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (21939817) 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, 10969905 + 10969906.

It is an arithmetic number, because the mean of its divisors is an integer number (10969906).

Almost surely, 2^21939811 is an apocalyptic number.

21939811 is a deficient number, since it is larger than the sum of its proper divisors (1).

21939811 is an equidigital number, since it uses as much as digits as its factorization.

21939811 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3888, while the sum is 34.

The square root of 21939811 is about 4683.9951964109. The cubic root of 21939811 is about 279.9481664256.

The spelling of 21939811 in words is "twenty-one million, nine hundred thirty-nine thousand, eight hundred eleven".