21994643 has 4 divisors (see below), whose sum is σ = 23994168. Its totient is φ = 19995120.

The previous prime is 21994607. The next prime is 21994657. The reversal of 21994643 is 34649912.

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 21994643 - 2¹⁰ = 21993619 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21994597 and 21994606.

It is not an unprimeable number, because it can be changed into a prime (21994603) 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, 999746 + ... + 999767.

It is an arithmetic number, because the mean of its divisors is an integer number (5998542).

Almost surely, 2^21994643 is an apocalyptic number.

21994643 is a deficient number, since it is larger than the sum of its proper divisors (1999525).

21994643 is a wasteful number, since it uses less digits than its factorization.

21994643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1999524.

The product of its digits is 46656, while the sum is 38.

The square root of 21994643 is about 4689.8446669373. The cubic root of 21994643 is about 280.1811880001.

The spelling of 21994643 in words is "twenty-one million, nine hundred ninety-four thousand, six hundred forty-three".