21197663 has 4 divisors (see below), whose sum is σ = 21395880. Its totient is φ = 20999448.

The previous prime is 21197653. The next prime is 21197677. The reversal of 21197663 is 36679112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21197663 - 2¹⁶ = 21132127 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21197653) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 98948 + ... + 99161.

It is an arithmetic number, because the mean of its divisors is an integer number (5348970).

Almost surely, 2^21197663 is an apocalyptic number.

21197663 is a deficient number, since it is larger than the sum of its proper divisors (198217).

21197663 is a wasteful number, since it uses less digits than its factorization.

21197663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 198216.

The product of its digits is 13608, while the sum is 35.

The square root of 21197663 is about 4604.0919843113. The cubic root of 21197663 is about 276.7553305285.

The spelling of 21197663 in words is "twenty-one million, one hundred ninety-seven thousand, six hundred sixty-three".