20813985 has 24 divisors (see below), whose sum is σ = 36489960. Its totient is φ = 10973952.

The previous prime is 20813983. The next prime is 20814023. The reversal of 20813985 is 58931802.

It can be written as a sum of positive squares in 4 ways, for example, as 374544 + 20439441 = 612^2 + 4521^2 .

It is not a de Polignac number, because 20813985 - 2¹ = 20813983 is a prime.

It is a super-4 number, since 4×20813985⁴ (a number of 30 digits) contains 4444 as substring.

It is not an unprimeable number, because it can be changed into a prime (20813983) 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, 1407 + ... + 6603.

It is an arithmetic number, because the mean of its divisors is an integer number (1520415).

Almost surely, 2^20813985 is an apocalyptic number.

It is an amenable number.

20813985 is a deficient number, since it is larger than the sum of its proper divisors (15675975).

20813985 is a wasteful number, since it uses less digits than its factorization.

20813985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5297 (or 5294 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The square root of 20813985 is about 4562.2346498180. The cubic root of 20813985 is about 275.0753953053.

The spelling of 20813985 in words is "twenty million, eight hundred thirteen thousand, nine hundred eighty-five".