21993943 has 4 divisors (see below), whose sum is σ = 22054240. Its totient is φ = 21933648.

The previous prime is 21993893. The next prime is 21993949. The reversal of 21993943 is 34939912.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21993943 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21993896 and 21993905.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21993949) 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, 29598 + ... + 30331.

It is an arithmetic number, because the mean of its divisors is an integer number (5513560).

Almost surely, 2^21993943 is an apocalyptic number.

21993943 is a deficient number, since it is larger than the sum of its proper divisors (60297).

21993943 is an equidigital number, since it uses as much as digits as its factorization.

21993943 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60296.

The product of its digits is 52488, while the sum is 40.

The square root of 21993943 is about 4689.7700370061. The cubic root of 21993943 is about 280.1782156261.

The spelling of 21993943 in words is "twenty-one million, nine hundred ninety-three thousand, nine hundred forty-three".