21993647 has 8 divisors (see below), whose sum is σ = 23750160. Its totient is φ = 20246400.

The previous prime is 21993637. The next prime is 21993649. The reversal of 21993647 is 74639912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21993647 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 (21993649) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3104 + ... + 7322.

It is an arithmetic number, because the mean of its divisors is an integer number (2968770).

Almost surely, 2^21993647 is an apocalyptic number.

21993647 is a deficient number, since it is larger than the sum of its proper divisors (1756513).

21993647 is a wasteful number, since it uses less digits than its factorization.

21993647 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4633.

The product of its digits is 81648, while the sum is 41.

The square root of 21993647 is about 4689.7384788493. The cubic root of 21993647 is about 280.1769587176.

The spelling of 21993647 in words is "twenty-one million, nine hundred ninety-three thousand, six hundred forty-seven".