21606863 has 2 divisors, whose sum is σ = 21606864. Its totient is φ = 21606862.

The previous prime is 21606859. The next prime is 21606869. The reversal of 21606863 is 36860612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21606863 - 2² = 21606859 is a prime.

It is equal to p_1365917 and since 21606863 and 1365917 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 (21606869) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10803431 + 10803432.

It is an arithmetic number, because the mean of its divisors is an integer number (10803432).

Almost surely, 2^21606863 is an apocalyptic number.

21606863 is a deficient number, since it is larger than the sum of its proper divisors (1).

21606863 is an equidigital number, since it uses as much as digits as its factorization.

21606863 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10368, while the sum is 32.

The square root of 21606863 is about 4648.3182980515. The cubic root of 21606863 is about 278.5248224714.

The spelling of 21606863 in words is "twenty-one million, six hundred six thousand, eight hundred sixty-three".