20811391 has 2 divisors, whose sum is σ = 20811392. Its totient is φ = 20811390.

The previous prime is 20811379. The next prime is 20811397. The reversal of 20811391 is 19311802.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20811391 - 2⁵ = 20811359 is a prime.

It is a super-2 number, since 2×20811391² = 866227990709762, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20811397) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10405695 + 10405696.

It is an arithmetic number, because the mean of its divisors is an integer number (10405696).

Almost surely, 2^20811391 is an apocalyptic number.

20811391 is a deficient number, since it is larger than the sum of its proper divisors (1).

20811391 is an equidigital number, since it uses as much as digits as its factorization.

20811391 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 432, while the sum is 25.

The square root of 20811391 is about 4561.9503504532. The cubic root of 20811391 is about 275.0639674886.

The spelling of 20811391 in words is "twenty million, eight hundred eleven thousand, three hundred ninety-one".