20606821 has 4 divisors (see below), whose sum is σ = 21045312. Its totient is φ = 20168332.

The previous prime is 20606813. The next prime is 20606857. The reversal of 20606821 is 12860602.

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 20606821 - 2³ = 20606813 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 (20606801) 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, 219175 + ... + 219268.

It is an arithmetic number, because the mean of its divisors is an integer number (5261328).

Almost surely, 2^20606821 is an apocalyptic number.

It is an amenable number.

20606821 is a deficient number, since it is larger than the sum of its proper divisors (438491).

20606821 is an equidigital number, since it uses as much as digits as its factorization.

20606821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 438490.

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 20606821 is about 4539.4736479024. The cubic root of 20606821 is about 274.1597315754.

It can be divided in two parts, 20 and 606821, that added together give a square (606841 = 779²).

The spelling of 20606821 in words is "twenty million, six hundred six thousand, eight hundred twenty-one".