20711561 has 4 divisors (see below), whose sum is σ = 22304772. Its totient is φ = 19118352.

The previous prime is 20711557. The next prime is 20711563. The reversal of 20711561 is 16511702.

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 855625 + 19855936 = 925^2 + 4456^2 .

It is a cyclic number.

It is not a de Polignac number, because 20711561 - 2² = 20711557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20711563) 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, 796586 + ... + 796611.

It is an arithmetic number, because the mean of its divisors is an integer number (5576193).

Almost surely, 2^20711561 is an apocalyptic number.

It is an amenable number.

20711561 is a deficient number, since it is larger than the sum of its proper divisors (1593211).

20711561 is a wasteful number, since it uses less digits than its factorization.

20711561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1593210.

The product of its (nonzero) digits is 420, while the sum is 23.

The square root of 20711561 is about 4550.9956053593. The cubic root of 20711561 is about 274.6234449525.

The spelling of 20711561 in words is "twenty million, seven hundred eleven thousand, five hundred sixty-one".