21993043 has 4 divisors (see below), whose sum is σ = 22702528. Its totient is φ = 21283560.

The previous prime is 21993007. The next prime is 21993067. The reversal of 21993043 is 34039912.

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 21993043 - 2¹⁷ = 21861971 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31), and also a Moran number because the ratio is a prime number: 709453 = 21993043 / (2 + 1 + 9 + 9 + 3 + 0 + 4 + 3).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21992996 and 21993014.

It is not an unprimeable number, because it can be changed into a prime (21993073) 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, 354696 + ... + 354757.

It is an arithmetic number, because the mean of its divisors is an integer number (5675632).

Almost surely, 2^21993043 is an apocalyptic number.

21993043 is a deficient number, since it is larger than the sum of its proper divisors (709485).

21993043 is an equidigital number, since it uses as much as digits as its factorization.

21993043 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 709484.

The product of its (nonzero) digits is 5832, while the sum is 31.

The square root of 21993043 is about 4689.6740824923. The cubic root of 21993043 is about 280.1743939098.

The spelling of 21993043 in words is "twenty-one million, nine hundred ninety-three thousand, forty-three".