20585681 has 4 divisors (see below), whose sum is σ = 20595312. Its totient is φ = 20576052.

The previous prime is 20585659. The next prime is 20585687. The reversal of 20585681 is 18658502.

It is a happy number.

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, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 18658502 = 2 ⋅9329251.

It is a cyclic number.

It is not a de Polignac number, because 20585681 - 2²² = 16391377 is a prime.

It is a super-2 number, since 2×20585681² = 847540524467522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20585687) 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, 11 + ... + 6416.

It is an arithmetic number, because the mean of its divisors is an integer number (5148828).

Almost surely, 2^20585681 is an apocalyptic number.

It is an amenable number.

20585681 is a deficient number, since it is larger than the sum of its proper divisors (9631).

20585681 is an equidigital number, since it uses as much as digits as its factorization.

20585681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9630.

The product of its (nonzero) digits is 19200, while the sum is 35.

The square root of 20585681 is about 4537.1445866316. The cubic root of 20585681 is about 274.0659483931.

The spelling of 20585681 in words is "twenty million, five hundred eighty-five thousand, six hundred eighty-one".