21390911 has 2 divisors, whose sum is σ = 21390912. Its totient is φ = 21390910.

The previous prime is 21390871. The next prime is 21390977. The reversal of 21390911 is 11909312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21390911 - 2¹⁰ = 21389887 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21390011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10695455 + 10695456.

It is an arithmetic number, because the mean of its divisors is an integer number (10695456).

Almost surely, 2^21390911 is an apocalyptic number.

21390911 is a deficient number, since it is larger than the sum of its proper divisors (1).

21390911 is an equidigital number, since it uses as much as digits as its factorization.

21390911 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 486, while the sum is 26.

The square root of 21390911 is about 4625.0309188156. The cubic root of 21390911 is about 277.5937988784.

The spelling of 21390911 in words is "twenty-one million, three hundred ninety thousand, nine hundred eleven".