21634663 has 2 divisors, whose sum is σ = 21634664. Its totient is φ = 21634662.

The previous prime is 21634661. The next prime is 21634699. The reversal of 21634663 is 36643612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21634663 - 2¹ = 21634661 is a prime.

Together with 21634661, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21634661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10817331 + 10817332.

It is an arithmetic number, because the mean of its divisors is an integer number (10817332).

Almost surely, 2^21634663 is an apocalyptic number.

21634663 is a deficient number, since it is larger than the sum of its proper divisors (1).

21634663 is an equidigital number, since it uses as much as digits as its factorization.

21634663 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 31.

The square root of 21634663 is about 4651.3076655925. The cubic root of 21634663 is about 278.6442239111.

The spelling of 21634663 in words is "twenty-one million, six hundred thirty-four thousand, six hundred sixty-three".