21398593 has 4 divisors (see below), whose sum is σ = 21454848. Its totient is φ = 21342340.

The previous prime is 21398581. The next prime is 21398599. The reversal of 21398593 is 39589312.

It is the 1889-th star number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21398593 - 2⁵ = 21398561 is a prime.

It is a Smith number, since the sum of its digits (40) 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 (21398599) 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, 27553 + ... + 28318.

It is an arithmetic number, because the mean of its divisors is an integer number (5363712).

Almost surely, 2^21398593 is an apocalyptic number.

It is an amenable number.

21398593 is a deficient number, since it is larger than the sum of its proper divisors (56255).

21398593 is an equidigital number, since it uses as much as digits as its factorization.

21398593 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56254.

The product of its digits is 58320, while the sum is 40.

The square root of 21398593 is about 4625.8613252020. The cubic root of 21398593 is about 277.6270251451.

The spelling of 21398593 in words is "twenty-one million, three hundred ninety-eight thousand, five hundred ninety-three".