20609581 has 2 divisors, whose sum is σ = 20609582. Its totient is φ = 20609580.

The previous prime is 20609573. The next prime is 20609639. The reversal of 20609581 is 18590602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20475625 + 133956 = 4525^2 + 366^2 .

It is a cyclic number.

It is not a de Polignac number, because 20609581 - 2³ = 20609573 is a prime.

It is a super-2 number, since 2×20609581² = 849509657991122, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20604581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10304790 + 10304791.

It is an arithmetic number, because the mean of its divisors is an integer number (10304791).

Almost surely, 2^20609581 is an apocalyptic number.

It is an amenable number.

20609581 is a deficient number, since it is larger than the sum of its proper divisors (1).

20609581 is an equidigital number, since it uses as much as digits as its factorization.

20609581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4320, while the sum is 31.

The square root of 20609581 is about 4539.7776377263. Note that the first 3 decimals coincide. The cubic root of 20609581 is about 274.1719710030.

The spelling of 20609581 in words is "twenty million, six hundred nine thousand, five hundred eighty-one".