20520561 has 4 divisors (see below), whose sum is σ = 27360752. Its totient is φ = 13680372.

The previous prime is 20520557. The next prime is 20520569. The reversal of 20520561 is 16502502.

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 not a de Polignac number, because 20520561 - 2² = 20520557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20520569) 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 3 ways as a sum of consecutive naturals, for example, 3420091 + ... + 3420096.

It is an arithmetic number, because the mean of its divisors is an integer number (6840188).

Almost surely, 2^20520561 is an apocalyptic number.

It is an amenable number.

20520561 is a deficient number, since it is larger than the sum of its proper divisors (6840191).

20520561 is an equidigital number, since it uses as much as digits as its factorization.

20520561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6840190.

The product of its (nonzero) digits is 600, while the sum is 21.

The square root of 20520561 is about 4529.9625826269. The cubic root of 20520561 is about 273.7766530209.

The spelling of 20520561 in words is "twenty million, five hundred twenty thousand, five hundred sixty-one".