20865681 has 24 divisors (see below), whose sum is σ = 33100704. Its totient is φ = 13089600.

The previous prime is 20865671. The next prime is 20865701. The reversal of 20865681 is 18656802.

It is a happy number.

It is not a de Polignac number, because 20865681 - 2⁶ = 20865617 is a prime.

It is a super-2 number, since 2×20865681² = 870753287187522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (20865601) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1606 + ... + 6656.

It is an arithmetic number, because the mean of its divisors is an integer number (1379196).

Almost surely, 2^20865681 is an apocalyptic number.

It is an amenable number.

20865681 is a deficient number, since it is larger than the sum of its proper divisors (12235023).

20865681 is an equidigital number, since it uses as much as digits as its factorization.

20865681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5083 (or 5071 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 36.

The square root of 20865681 is about 4567.8967807953. The cubic root of 20865681 is about 275.3029432865.

The spelling of 20865681 in words is "twenty million, eight hundred sixty-five thousand, six hundred eighty-one".