20519561 has 4 divisors (see below), whose sum is σ = 21726612. Its totient is φ = 19312512.

The previous prime is 20519549. The next prime is 20519599. The reversal of 20519561 is 16591502.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16591502 = 2 ⋅8295751.

It can be written as a sum of positive squares in 2 ways, for example, as 12924025 + 7595536 = 3595^2 + 2756^2 .

It is a cyclic number.

It is not a de Polignac number, because 20519561 - 2¹⁴ = 20503177 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20519461) 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, 603500 + ... + 603533.

It is an arithmetic number, because the mean of its divisors is an integer number (5431653).

Almost surely, 2^20519561 is an apocalyptic number.

It is an amenable number.

20519561 is a deficient number, since it is larger than the sum of its proper divisors (1207051).

20519561 is a wasteful number, since it uses less digits than its factorization.

20519561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1207050.

The product of its (nonzero) digits is 2700, while the sum is 29.

The square root of 20519561 is about 4529.8522050946. The cubic root of 20519561 is about 273.7722057562.

The spelling of 20519561 in words is "twenty million, five hundred nineteen thousand, five hundred sixty-one".