21943391 has 2 divisors, whose sum is σ = 21943392. Its totient is φ = 21943390.

The previous prime is 21943387. The next prime is 21943399. The reversal of 21943391 is 19334912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21943391 - 2² = 21943387 is a prime.

It is a Chen prime.

It is equal to p_1385924 and since 21943391 and 1385924 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21943399) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10971695 + 10971696.

It is an arithmetic number, because the mean of its divisors is an integer number (10971696).

Almost surely, 2^21943391 is an apocalyptic number.

21943391 is a deficient number, since it is larger than the sum of its proper divisors (1).

21943391 is an equidigital number, since it uses as much as digits as its factorization.

21943391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5832, while the sum is 32.

The square root of 21943391 is about 4684.3773332216. The cubic root of 21943391 is about 279.9633923229.

The spelling of 21943391 in words is "twenty-one million, nine hundred forty-three thousand, three hundred ninety-one".