21993535 has 4 divisors (see below), whose sum is σ = 26392248. Its totient is φ = 17594824.

The previous prime is 21993527. The next prime is 21993541. The reversal of 21993535 is 53539912.

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 21993535 - 2³ = 21993527 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21993494 and 21993503.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2199349 + ... + 2199358.

It is an arithmetic number, because the mean of its divisors is an integer number (6598062).

Almost surely, 2^21993535 is an apocalyptic number.

21993535 is a deficient number, since it is larger than the sum of its proper divisors (4398713).

21993535 is an equidigital number, since it uses as much as digits as its factorization.

21993535 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4398712.

The product of its digits is 36450, while the sum is 37.

The square root of 21993535 is about 4689.7265378698. The cubic root of 21993535 is about 280.1764831276.

The spelling of 21993535 in words is "twenty-one million, nine hundred ninety-three thousand, five hundred thirty-five".