21606231 has 4 divisors (see below), whose sum is σ = 28808312. Its totient is φ = 14404152.

The previous prime is 21606217. The next prime is 21606259. The reversal of 21606231 is 13260612.

It is a happy number.

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

It is not a de Polignac number, because 21606231 - 2¹³ = 21598039 is a prime.

It is a super-2 number, since 2×21606231² = 933658436050722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21606198 and 21606207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21606271) 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, 3601036 + ... + 3601041.

It is an arithmetic number, because the mean of its divisors is an integer number (7202078).

Almost surely, 2^21606231 is an apocalyptic number.

21606231 is a deficient number, since it is larger than the sum of its proper divisors (7202081).

21606231 is an equidigital number, since it uses as much as digits as its factorization.

21606231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7202080.

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 21606231 is about 4648.2503159791. The cubic root of 21606231 is about 278.5221068311.

Adding to 21606231 its reverse (13260612), we get a palindrome (34866843).

The spelling of 21606231 in words is "twenty-one million, six hundred six thousand, two hundred thirty-one".