20865391 has 2 divisors, whose sum is σ = 20865392. Its totient is φ = 20865390.

The previous prime is 20865389. The next prime is 20865461. The reversal of 20865391 is 19356802.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20865391 - 2¹ = 20865389 is a prime.

Together with 20865389, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20865311) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10432695 + 10432696.

It is an arithmetic number, because the mean of its divisors is an integer number (10432696).

Almost surely, 2^20865391 is an apocalyptic number.

20865391 is a deficient number, since it is larger than the sum of its proper divisors (1).

20865391 is an equidigital number, since it uses as much as digits as its factorization.

20865391 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 20865391 is about 4567.8650374108. The cubic root of 20865391 is about 275.3016678553.

The spelling of 20865391 in words is "twenty million, eight hundred sixty-five thousand, three hundred ninety-one".