20122561 has 4 divisors (see below), whose sum is σ = 20666452. Its totient is φ = 19578672.

The previous prime is 20122559. The next prime is 20122589. The reversal of 20122561 is 16522102.

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

It can be written as a sum of positive squares in 2 ways, for example, as 13068225 + 7054336 = 3615^2 + 2656^2 .

It is a cyclic number.

It is not a de Polignac number, because 20122561 - 2¹ = 20122559 is a prime.

It is a super-3 number, since 3×20122561³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20122511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 271890 + ... + 271963.

It is an arithmetic number, because the mean of its divisors is an integer number (5166613).

Almost surely, 2^20122561 is an apocalyptic number.

It is an amenable number.

20122561 is a deficient number, since it is larger than the sum of its proper divisors (543891).

20122561 is an equidigital number, since it uses as much as digits as its factorization.

20122561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 543890.

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 20122561 is about 4485.8177626827. The cubic root of 20122561 is about 271.9951024565.

Adding to 20122561 its reverse (16522102), we get a palindrome (36644663).

The spelling of 20122561 in words is "twenty million, one hundred twenty-two thousand, five hundred sixty-one".