21593221 has 8 divisors (see below), whose sum is σ = 23337720. Its totient is φ = 19860672.

The previous prime is 21593203. The next prime is 21593239. The reversal of 21593221 is 12239512.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21593203) and next prime (21593239).

It can be written as a sum of positive squares in 4 ways, for example, as 2356225 + 19236996 = 1535^2 + 4386^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21593221 - 2⁵ = 21593189 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21593261) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 975 + ... + 6643.

It is an arithmetic number, because the mean of its divisors is an integer number (2917215).

Almost surely, 2^21593221 is an apocalyptic number.

It is an amenable number.

21593221 is a deficient number, since it is larger than the sum of its proper divisors (1744499).

21593221 is a wasteful number, since it uses less digits than its factorization.

21593221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5975.

The product of its digits is 1080, while the sum is 25.

The square root of 21593221 is about 4646.8506539376. The cubic root of 21593221 is about 278.4661924029.

The spelling of 21593221 in words is "twenty-one million, five hundred ninety-three thousand, two hundred twenty-one".