20609921 has 6 divisors (see below), whose sum is σ = 21142422. Its totient is φ = 20078880.

The previous prime is 20609917. The next prime is 20609929. The reversal of 20609921 is 12990602.

It can be written as a sum of positive squares in 3 ways, for example, as 1809025 + 18800896 = 1345^2 + 4336^2 .

It is not a de Polignac number, because 20609921 - 2² = 20609917 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 (20609929) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 28715 + ... + 29423.

It is an arithmetic number, because the mean of its divisors is an integer number (3523737).

Almost surely, 2^20609921 is an apocalyptic number.

It is an amenable number.

20609921 is a deficient number, since it is larger than the sum of its proper divisors (532501).

20609921 is an frugal number, since it uses more digits than its factorization.

20609921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1459 (or 750 counting only the distinct ones).

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 20609921 is about 4539.8150843399. The cubic root of 20609921 is about 274.1734786830.

The spelling of 20609921 in words is "twenty million, six hundred nine thousand, nine hundred twenty-one".