21399563 has 2 divisors, whose sum is σ = 21399564. Its totient is φ = 21399562.

The previous prime is 21399559. The next prime is 21399649. The reversal of 21399563 is 36599312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21399563 - 2² = 21399559 is a prime.

It is not a weakly prime, because it can be changed into another prime (21399503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10699781 + 10699782.

It is an arithmetic number, because the mean of its divisors is an integer number (10699782).

Almost surely, 2^21399563 is an apocalyptic number.

21399563 is a deficient number, since it is larger than the sum of its proper divisors (1).

21399563 is an equidigital number, since it uses as much as digits as its factorization.

21399563 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 43740, while the sum is 38.

The square root of 21399563 is about 4625.9661693532. The cubic root of 21399563 is about 277.6312200338.

The spelling of 21399563 in words is "twenty-one million, three hundred ninety-nine thousand, five hundred sixty-three".