21304993 has 4 divisors (see below), whose sum is σ = 21707028. Its totient is φ = 20902960.

The previous prime is 21304991. The next prime is 21305003. The reversal of 21304993 is 39940312.

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

It can be written as a sum of positive squares in 2 ways, for example, as 19607184 + 1697809 = 4428^2 + 1303^2 .

It is a cyclic number.

It is not a de Polignac number, because 21304993 - 2¹ = 21304991 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21304991) 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, 200938 + ... + 201043.

It is an arithmetic number, because the mean of its divisors is an integer number (5426757).

Almost surely, 2^21304993 is an apocalyptic number.

It is an amenable number.

21304993 is a deficient number, since it is larger than the sum of its proper divisors (402035).

21304993 is an equidigital number, since it uses as much as digits as its factorization.

21304993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 402034.

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

The square root of 21304993 is about 4615.7332028617. The cubic root of 21304993 is about 277.2216422561.

The spelling of 21304993 in words is "twenty-one million, three hundred four thousand, nine hundred ninety-three".