21943387 has 2 divisors, whose sum is σ = 21943388. Its totient is φ = 21943386.

The previous prime is 21943351. The next prime is 21943391. The reversal of 21943387 is 78334912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21943387 - 2¹⁵ = 21910619 is a prime.

It is not a weakly prime, because it can be changed into another prime (21943087) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10971693 + 10971694.

It is an arithmetic number, because the mean of its divisors is an integer number (10971694).

Almost surely, 2^21943387 is an apocalyptic number.

21943387 is a deficient number, since it is larger than the sum of its proper divisors (1).

21943387 is an equidigital number, since it uses as much as digits as its factorization.

21943387 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36288, while the sum is 37.

The square root of 21943387 is about 4684.3769062705. The cubic root of 21943387 is about 279.9633753117.

The spelling of 21943387 in words is "twenty-one million, nine hundred forty-three thousand, three hundred eighty-seven".