21379927 has 2 divisors, whose sum is σ = 21379928. Its totient is φ = 21379926.

The previous prime is 21379913. The next prime is 21379933. The reversal of 21379927 is 72997312.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21379927 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21379927.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21379907) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10689963 + 10689964.

It is an arithmetic number, because the mean of its divisors is an integer number (10689964).

Almost surely, 2^21379927 is an apocalyptic number.

21379927 is a deficient number, since it is larger than the sum of its proper divisors (1).

21379927 is an equidigital number, since it uses as much as digits as its factorization.

21379927 is an evil number, because the sum of its binary digits is even.

The product of its digits is 47628, while the sum is 40.

The square root of 21379927 is about 4623.8433148194. The cubic root of 21379927 is about 277.5462769453.

The spelling of 21379927 in words is "twenty-one million, three hundred seventy-nine thousand, nine hundred twenty-seven".